diff --git a/README.md b/README.md
index 7cf8b6b8..de3348e5 100644
--- a/README.md
+++ b/README.md
@@ -16,9 +16,7 @@ $ npm install gaxios
 
 ```js
 const {request} = require('gaxios');
-const res = await request({
-  url: 'https://www.googleapis.com/discovery/v1/apis/',
-});
+const res = await request('https://www.googleapis.com/discovery/v1/apis/');
 ```
 
 ## Setting Defaults
@@ -53,16 +51,26 @@ interface GaxiosOptions = {
   baseURL: 'https://example.com';
 
   // The HTTP methods to be sent with the request.
-  headers: { 'some': 'header' },
-
-  // The data to send in the body of the request. Data objects will be
-  // serialized as JSON.
+  headers: { 'some': 'header' } || new Headers(),
+
+  // The data to send in the body of the request. Objects will be serialized as JSON
+  // except for:
+  // - `ArrayBuffer`
+  // - `Blob`
+  // - `Buffer` (Node.js)
+  // - `DataView`
+  // - `File`
+  // - `FormData`
+  // - `ReadableStream`
+  // - `stream.Readable` (Node.js)
+  // - strings
+  // - `TypedArray` (e.g. `Uint8Array`, `BigInt64Array`)
+  // - `URLSearchParams`
+  // - all other objects where:
+  //   - headers['Content-Type'] === 'application/x-www-form-urlencoded' (serialized as `URLSearchParams`)
   //
-  // Note: if you would like to provide a Content-Type header other than
-  // application/json you you must provide a string or readable stream, rather
-  // than an object:
-  // data: JSON.stringify({some: 'data'})
-  // data: fs.readFile('./some-data.jpeg')
+  // In all other cases, if you would like to prevent `application/json` as the
+  // default you must set the `Content-Type` header.
   data: {
     some: 'data'
   },
@@ -71,23 +79,12 @@ interface GaxiosOptions = {
   // Defaults to `0`, which is the same as unset.
   maxContentLength: 2000,
 
-  // The max number of HTTP redirects to follow.
-  // Defaults to 100.
-  maxRedirects: 100,
-
-  // The querystring parameters that will be encoded using `qs` and
+  // The query parameters that will be encoded using `URLSearchParams` and
   // appended to the url
   params: {
     querystring: 'parameters'
   },
 
-  // By default, we use the `querystring` package in node core to serialize
-  // querystring parameters.  You can override that and provide your
-  // own implementation.
-  paramsSerializer: (params) => {
-    return qs.stringify(params);
-  },
-
   // The timeout for the HTTP request in milliseconds. Defaults to 0.
   timeout: 1000,
 
@@ -105,6 +102,8 @@ interface GaxiosOptions = {
   // The expected return type of the request.  Options are:
   // json | stream | blob | arraybuffer | text | unknown
   // Defaults to `unknown`.
+  // If the `fetchImplementation` is native `fetch`, the
+  // stream is a `ReadableStream`, otherwise `readable.Stream`
   responseType: 'unknown',
 
   // The node.js http agent to use for the request.
@@ -114,9 +113,9 @@ interface GaxiosOptions = {
   // status code.  Defaults to (>= 200 && < 300)
   validateStatus: (status: number) => true,
 
-  // Implementation of `fetch` to use when making the API call. By default,
-  // will use the browser context if available, and fall back to `node-fetch`
-  // in node.js otherwise.
+  /**
+   * Implementation of `fetch` to use when making the API call. Will use `fetch` by default.
+   */
   fetchImplementation?: typeof fetch;
 
   // Configuration for retrying of requests.
@@ -151,8 +150,7 @@ interface GaxiosOptions = {
   // Enables default configuration for retries.
   retry: boolean,
 
-  // Cancelling a request requires the `abort-controller` library.
-  // See https://github.com/bitinn/node-fetch#request-cancellation-with-abortsignal
+  // Enables aborting via AbortController
   signal?: AbortSignal
 
   /**
diff --git a/browser-test/test.browser.ts b/browser-test/test.browser.ts
index 06d926e0..41b2ccb3 100644
--- a/browser-test/test.browser.ts
+++ b/browser-test/test.browser.ts
@@ -14,7 +14,6 @@
 import assert from 'assert';
 import {describe, it} from 'mocha';
 import {request} from '../src/index';
-import * as uuid from 'uuid';
 const port = 7172; // should match the port defined in `webserver.ts`
 
 describe('💻 browser tests', () => {
@@ -53,7 +52,8 @@ describe('💻 browser tests', () => {
         body: 'hello world!',
       },
     ];
-    const boundary = uuid.v4();
+    const boundary =
+      globalThis?.crypto.randomUUID() || (await import('crypto')).randomUUID();
     const finale = `--${boundary}--`;
     headers['Content-Type'] = `multipart/related; boundary=${boundary}`;
 
diff --git a/package.json b/package.json
index f81f6e63..f7e433ca 100644
--- a/package.json
+++ b/package.json
@@ -47,18 +47,14 @@
     "@types/mv": "^2.1.0",
     "@types/ncp": "^2.0.1",
     "@types/node": "^20.0.0",
-    "@types/node-fetch": "^2.5.7",
     "@types/sinon": "^17.0.0",
     "@types/tmp": "0.2.6",
-    "@types/uuid": "^10.0.0",
-    "abort-controller": "^3.0.0",
     "assert": "^2.0.0",
     "browserify": "^17.0.0",
     "c8": "^8.0.0",
     "cors": "^2.8.5",
     "execa": "^5.0.0",
     "express": "^4.16.4",
-    "form-data": "^4.0.0",
     "gts": "^5.0.0",
     "is-docker": "^2.0.0",
     "karma": "^6.0.0",
@@ -74,7 +70,7 @@
     "multiparty": "^4.2.1",
     "mv": "^2.1.1",
     "ncp": "^2.0.0",
-    "nock": "^13.0.0",
+    "nock": "^14.0.0-beta.13",
     "null-loader": "^4.0.0",
     "puppeteer": "^19.0.0",
     "sinon": "^18.0.0",
@@ -88,8 +84,6 @@
   "dependencies": {
     "extend": "^3.0.2",
     "https-proxy-agent": "^7.0.1",
-    "is-stream": "^2.0.0",
-    "node-fetch": "^2.6.9",
-    "uuid": "^10.0.0"
+    "node-fetch": "^3.3.2"
   }
 }
diff --git a/src/common.ts b/src/common.ts
index b1bedf6d..907027f0 100644
--- a/src/common.ts
+++ b/src/common.ts
@@ -77,7 +77,7 @@ export class GaxiosError<T = any> extends Error {
 
   constructor(
     message: string,
-    public config: GaxiosOptions,
+    public config: GaxiosOptionsPrepared,
     public response?: GaxiosResponse<T>,
     public error?: Error | NodeJS.ErrnoException
   ) {
@@ -94,7 +94,8 @@ export class GaxiosError<T = any> extends Error {
       try {
         this.response.data = translateData(
           this.config.responseType,
-          this.response?.data
+          // workaround for `node-fetch`'s `.data` deprecation...
+          this.response?.bodyUsed ? this.response?.data : undefined
         );
       } catch {
         // best effort - don't throw an error within an error
@@ -110,7 +111,7 @@ export class GaxiosError<T = any> extends Error {
     }
 
     if (config.errorRedactor) {
-      config.errorRedactor<T>({
+      config.errorRedactor({
         config: this.config,
         response: this.response,
       });
@@ -118,40 +119,35 @@ export class GaxiosError<T = any> extends Error {
   }
 }
 
-export interface Headers {
-  [index: string]: any;
-}
-export type GaxiosPromise<T = any> = Promise<GaxiosResponse<T>>;
+type GaxiosResponseData =
+  | ReturnType<JSON['parse']>
+  | GaxiosOptionsPrepared['data'];
 
-export interface GaxiosXMLHttpRequest {
-  responseURL: string;
-}
+export type GaxiosPromise<T = GaxiosResponseData> = Promise<GaxiosResponse<T>>;
 
-export interface GaxiosResponse<T = any> {
-  config: GaxiosOptions;
+export interface GaxiosResponse<T = GaxiosResponseData> extends Response {
+  config: GaxiosOptionsPrepared;
   data: T;
-  status: number;
-  statusText: string;
-  headers: Headers;
-  request: GaxiosXMLHttpRequest;
 }
 
 export interface GaxiosMultipartOptions {
-  headers: Headers;
+  headers: HeadersInit;
   content: string | Readable;
 }
 
 /**
  * Request options that are used to form the request.
  */
-export interface GaxiosOptions {
+export interface GaxiosOptions extends RequestInit {
   /**
    * Optional method to override making the actual HTTP request. Useful
    * for writing tests.
+   *
+   * @deprecated Use {@link GaxiosOptions.fetchImplementation} instead.
    */
-  adapter?: <T = any>(
-    options: GaxiosOptions,
-    defaultAdapter: (options: GaxiosOptions) => GaxiosPromise<T>
+  adapter?: <T = GaxiosResponseData>(
+    options: GaxiosOptionsPrepared,
+    defaultAdapter: (options: GaxiosOptionsPrepared) => GaxiosPromise<T>
   ) => GaxiosPromise<T>;
   url?: string | URL;
   /**
@@ -159,39 +155,75 @@ export interface GaxiosOptions {
    */
   baseUrl?: string;
   baseURL?: string | URL;
-  method?:
-    | 'GET'
-    | 'HEAD'
-    | 'POST'
-    | 'DELETE'
-    | 'PUT'
-    | 'CONNECT'
-    | 'OPTIONS'
-    | 'TRACE'
-    | 'PATCH';
-  headers?: Headers;
-  data?: any;
-  body?: any;
   /**
-   * The maximum size of the http response content in bytes allowed.
+   * The data to send in the {@link RequestInit.body} of the request. Objects will be
+   * serialized as JSON, except for:
+   * - `ArrayBuffer`
+   * - `Blob`
+   * - `Buffer` (Node.js)
+   * - `DataView`
+   * - `File`
+   * - `FormData`
+   * - `ReadableStream`
+   * - `stream.Readable` (Node.js)
+   * - strings
+   * - `TypedArray` (e.g. `Uint8Array`, `BigInt64Array`)
+   * - `URLSearchParams`
+   * - all other objects where:
+   *   - headers['Content-Type'] === 'application/x-www-form-urlencoded' (serialized as `URLSearchParams`)
+   *
+   * In all other cases, if you would like to prevent `application/json` as the
+   * default you must set the `Content-Type` header.
+   */
+  data?:
+    | ArrayBuffer
+    | Blob
+    | Buffer
+    | DataView
+    | File
+    | FormData
+    | ReadableStream
+    | Readable
+    | string
+    | ArrayBufferView
+    | {buffer: ArrayBufferLike}
+    | URLSearchParams
+    | {}
+    | BodyInit;
+  /**
+   * The maximum size of the http response `Content-Length` in bytes allowed.
    */
   maxContentLength?: number;
   /**
    * The maximum number of redirects to follow. Defaults to 20.
+   *
+   * @deprecated non-spec. Should use `20` if enabled per-spec: https://fetch.spec.whatwg.org/#http-redirect-fetch
    */
   maxRedirects?: number;
+  /**
+   * @deprecated non-spec. Should use `20` if enabled per-spec: https://fetch.spec.whatwg.org/#http-redirect-fetch
+   */
   follow?: number;
   /**
    * A collection of parts to send as a `Content-Type: multipart/related` request.
+   *
+   * This is passed to {@link RequestInit.body}.
    */
   multipart?: GaxiosMultipartOptions[];
-  params?: any;
+  params?: GaxiosResponseData;
+  /**
+   * @deprecated Use {@link URLSearchParams} instead and pass this directly to {@link GaxiosOptions.data `data`}.
+   */
   paramsSerializer?: (params: {[index: string]: string | number}) => string;
   timeout?: number;
   /**
    * @deprecated ignored
    */
-  onUploadProgress?: (progressEvent: any) => void;
+  onUploadProgress?: (progressEvent: GaxiosResponseData) => void;
+  /**
+   * If the `fetchImplementation` is native `fetch`, the
+   * stream is a `ReadableStream`, otherwise `readable.Stream`
+   */
   responseType?:
     | 'arraybuffer'
     | 'blob'
@@ -203,16 +235,28 @@ export interface GaxiosOptions {
   validateStatus?: (status: number) => boolean;
   retryConfig?: RetryConfig;
   retry?: boolean;
-  // Should be instance of https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal
-  // interface. Left as 'any' due to incompatibility between spec and abort-controller.
-  signal?: any;
+  /**
+   * Enables aborting via {@link AbortController}.
+   */
+  signal?: AbortSignal;
+  /**
+   * @deprecated non-spec. https://github.com/node-fetch/node-fetch/issues/1438
+   */
   size?: number;
   /**
-   * Implementation of `fetch` to use when making the API call. By default,
-   * will use the browser context if available, and fall back to `node-fetch`
-   * in node.js otherwise.
+   * Implementation of `fetch` to use when making the API call. Will use `fetch` by default.
+   *
+   * @example
+   *
+   * let customFetchCalled = false;
+   * const myFetch = (...args: Parameters<typeof fetch>) => {
+   *  customFetchCalled = true;
+   *  return fetch(...args);
+   * };
+   *
+   * {fetchImplementation: myFetch};
    */
-  fetchImplementation?: FetchImplementation;
+  fetchImplementation?: typeof fetch;
   // Configure client to use mTLS:
   cert?: string;
   key?: string;
@@ -258,27 +302,14 @@ export interface GaxiosOptions {
    */
   errorRedactor?: typeof defaultErrorRedactor | false;
 }
-/**
- * A partial object of `GaxiosResponse` with only redactable keys
- *
- * @experimental
- */
-export type RedactableGaxiosOptions = Pick<
-  GaxiosOptions,
-  'body' | 'data' | 'headers' | 'url'
->;
-/**
- * A partial object of `GaxiosResponse` with only redactable keys
- *
- * @experimental
- */
-export type RedactableGaxiosResponse<T = any> = Pick<
-  GaxiosResponse<T>,
-  'config' | 'data' | 'headers'
->;
+
+export interface GaxiosOptionsPrepared extends GaxiosOptions {
+  headers: globalThis.Headers;
+  url: URL;
+}
 
 /**
- * Configuration for the Gaxios `request` method.
+ * Gaxios retry configuration.
  */
 export interface RetryConfig {
   /**
@@ -359,42 +390,10 @@ export interface RetryConfig {
   retryDelayMultiplier?: number;
 }
 
-export type FetchImplementation = (
-  input: FetchRequestInfo,
-  init?: FetchRequestInit
-) => Promise<FetchResponse>;
-
-export type FetchRequestInfo = any;
-
-export interface FetchResponse {
-  readonly status: number;
-  readonly statusText: string;
-  readonly url: string;
-  readonly body: unknown | null;
-  arrayBuffer(): Promise<unknown>;
-  blob(): Promise<unknown>;
-  readonly headers: FetchHeaders;
-  json(): Promise<any>;
-  text(): Promise<string>;
-}
-
-export interface FetchRequestInit {
-  method?: string;
-}
-
-export interface FetchHeaders {
-  append(name: string, value: string): void;
-  delete(name: string): void;
-  get(name: string): string | null;
-  has(name: string): boolean;
-  set(name: string, value: string): void;
-  forEach(
-    callbackfn: (value: string, key: string) => void,
-    thisArg?: any
-  ): void;
-}
-
-function translateData(responseType: string | undefined, data: any) {
+function translateData(
+  responseType: string | undefined,
+  data: GaxiosResponseData
+) {
   switch (responseType) {
     case 'stream':
       return data;
@@ -417,54 +416,62 @@ function translateData(responseType: string | undefined, data: any) {
  *
  * @experimental
  */
-export function defaultErrorRedactor<T = any>(data: {
-  config?: RedactableGaxiosOptions;
-  response?: RedactableGaxiosResponse<T>;
-}) {
+export function defaultErrorRedactor<
+  O extends GaxiosOptionsPrepared,
+  R extends GaxiosResponse<GaxiosResponseData>,
+>(data: {config?: O; response?: R}) {
   const REDACT =
     '<<REDACTED> - See `errorRedactor` option in `gaxios` for configuration>.';
 
   function redactHeaders(headers?: Headers) {
     if (!headers) return;
 
-    for (const key of Object.keys(headers)) {
+    headers.forEach((_, key) => {
       // any casing of `Authentication`
-      if (/^authentication$/i.test(key)) {
-        headers[key] = REDACT;
-      }
-
       // any casing of `Authorization`
-      if (/^authorization$/i.test(key)) {
-        headers[key] = REDACT;
-      }
-
       // anything containing secret, such as 'client secret'
-      if (/secret/i.test(key)) {
-        headers[key] = REDACT;
-      }
-    }
+      if (
+        /^authentication$/i.test(key) ||
+        /^authorization$/i.test(key) ||
+        /secret/i.test(key)
+      )
+        headers.set(key, REDACT);
+    });
   }
 
-  function redactString(obj: GaxiosOptions, key: keyof GaxiosOptions) {
+  function redactString<T extends O | R>(obj: T, key: keyof T) {
     if (
       typeof obj === 'object' &&
       obj !== null &&
       typeof obj[key] === 'string'
     ) {
-      const text = obj[key];
+      const text = obj[key] as string;
 
       if (
         /grant_type=/i.test(text) ||
         /assertion=/i.test(text) ||
         /secret/i.test(text)
       ) {
-        obj[key] = REDACT;
+        (obj[key] as {}) = REDACT;
       }
     }
   }
 
-  function redactObject<T extends GaxiosOptions['data']>(obj: T) {
-    if (typeof obj === 'object' && obj !== null) {
+  function redactObject<T extends O['data'] | R>(obj: T | null) {
+    if (!obj) {
+      return;
+    } else if (
+      obj instanceof FormData ||
+      obj instanceof URLSearchParams ||
+      // support `node-fetch` FormData/URLSearchParams
+      ('forEach' in obj && 'set' in obj)
+    ) {
+      (obj as FormData | URLSearchParams).forEach((_, key) => {
+        if (['grant_type', 'assertion'].includes(key) || /secret/.test(key)) {
+          (obj as FormData | URLSearchParams).set(key, REDACT);
+        }
+      });
+    } else {
       if ('grant_type' in obj) {
         obj['grant_type'] = REDACT;
       }
@@ -488,20 +495,12 @@ export function defaultErrorRedactor<T = any>(data: {
     redactString(data.config, 'body');
     redactObject(data.config.body);
 
-    try {
-      const url = new URL('', data.config.url);
-
-      if (url.searchParams.has('token')) {
-        url.searchParams.set('token', REDACT);
-      }
-
-      if (url.searchParams.has('client_secret')) {
-        url.searchParams.set('client_secret', REDACT);
-      }
+    if (data.config.url.searchParams.has('token')) {
+      data.config.url.searchParams.set('token', REDACT);
+    }
 
-      data.config.url = url.toString();
-    } catch {
-      // ignore error - no need to parse an invalid URL
+    if (data.config.url.searchParams.has('client_secret')) {
+      data.config.url.searchParams.set('client_secret', REDACT);
     }
   }
 
@@ -509,8 +508,11 @@ export function defaultErrorRedactor<T = any>(data: {
     defaultErrorRedactor({config: data.response.config});
     redactHeaders(data.response.headers);
 
-    redactString(data.response, 'data');
-    redactObject(data.response.data);
+    // workaround for `node-fetch`'s `.data` deprecation...
+    if ((data.response as {} as Response).bodyUsed) {
+      redactString(data.response, 'data');
+      redactObject(data.response.data);
+    }
   }
 
   return data;
diff --git a/src/gaxios.ts b/src/gaxios.ts
index 987644df..4787053f 100644
--- a/src/gaxios.ts
+++ b/src/gaxios.ts
@@ -14,55 +14,26 @@
 import extend from 'extend';
 import {Agent} from 'http';
 import {Agent as HTTPSAgent} from 'https';
-import nodeFetch from 'node-fetch';
-import qs from 'querystring';
-import isStream from 'is-stream';
 import {URL} from 'url';
+import type nodeFetch from 'node-fetch' with {'resolution-mode': 'import'};
 
 import {
-  FetchResponse,
   GaxiosMultipartOptions,
   GaxiosError,
   GaxiosOptions,
+  GaxiosOptionsPrepared,
   GaxiosPromise,
   GaxiosResponse,
-  Headers,
   defaultErrorRedactor,
 } from './common';
 import {getRetryConfig} from './retry';
-import {PassThrough, Stream, pipeline} from 'stream';
-import {v4} from 'uuid';
+import {Readable} from 'stream';
 import {GaxiosInterceptorManager} from './interceptor';
 
 /* eslint-disable @typescript-eslint/no-explicit-any */
 
-const fetch = hasFetch() ? window.fetch : nodeFetch;
-
-function hasWindow() {
-  return typeof window !== 'undefined' && !!window;
-}
-
-function hasFetch() {
-  return hasWindow() && !!window.fetch;
-}
-
-function hasBuffer() {
-  return typeof Buffer !== 'undefined';
-}
-
-function hasHeader(options: GaxiosOptions, header: string) {
-  return !!getHeader(options, header);
-}
-
-function getHeader(options: GaxiosOptions, header: string): string | undefined {
-  header = header.toLowerCase();
-  for (const key of Object.keys(options?.headers || {})) {
-    if (header === key.toLowerCase()) {
-      return options.headers![key];
-    }
-  }
-  return undefined;
-}
+const randomUUID = async () =>
+  globalThis.crypto?.randomUUID() || (await import('crypto')).randomUUID();
 
 export class Gaxios {
   protected agentCache = new Map<
@@ -79,7 +50,7 @@ export class Gaxios {
    * Interceptors
    */
   interceptors: {
-    request: GaxiosInterceptorManager<GaxiosOptions>;
+    request: GaxiosInterceptorManager<GaxiosOptionsPrepared>;
     response: GaxiosInterceptorManager<GaxiosResponse>;
   };
 
@@ -100,18 +71,41 @@ export class Gaxios {
    * @param opts Set of HTTP options that will be used for this HTTP request.
    */
   async request<T = any>(opts: GaxiosOptions = {}): GaxiosPromise<T> {
-    opts = await this.#prepareRequest(opts);
-    opts = await this.#applyRequestInterceptors(opts);
-    return this.#applyResponseInterceptors(this._request(opts));
+    let prepared = await this.#prepareRequest(opts);
+    prepared = await this.#applyRequestInterceptors(prepared);
+    return this.#applyResponseInterceptors(this._request(prepared));
   }
 
   private async _defaultAdapter<T>(
-    opts: GaxiosOptions
+    config: GaxiosOptionsPrepared
   ): Promise<GaxiosResponse<T>> {
-    const fetchImpl = opts.fetchImplementation || fetch;
-    const res = (await fetchImpl(opts.url, opts)) as FetchResponse;
-    const data = await this.getResponseData(opts, res);
-    return this.translateResponse<T>(opts, res, data);
+    const fetchImpl =
+      config.fetchImplementation ||
+      this.defaults.fetchImplementation ||
+      (await Gaxios.#getFetch());
+
+    // node-fetch v3 warns when `data` is present
+    // https://github.com/node-fetch/node-fetch/issues/1000
+    const preparedOpts = {...config};
+    delete preparedOpts.data;
+
+    const res = (await fetchImpl(config.url, preparedOpts as {})) as Response;
+    const data = await this.getResponseData(config, res);
+
+    // `node-fetch`'s data isn't writable. Native `fetch`'s is.
+    if (!Object.getOwnPropertyDescriptor(res, 'data')?.configurable) {
+      Object.defineProperties(res, {
+        data: {
+          configurable: true,
+          writable: true,
+          enumerable: true,
+          value: data,
+        },
+      });
+    }
+
+    // Keep object as an instance of `Response`
+    return Object.assign(res, {config, data});
   }
 
   /**
@@ -119,7 +113,7 @@ export class Gaxios {
    * @param opts Set of HTTP options that will be used for this HTTP request.
    */
   protected async _request<T = any>(
-    opts: GaxiosOptions = {}
+    opts: GaxiosOptionsPrepared
   ): GaxiosPromise<T> {
     try {
       let translatedResponse: GaxiosResponse<T>;
@@ -134,13 +128,12 @@ export class Gaxios {
 
       if (!opts.validateStatus!(translatedResponse.status)) {
         if (opts.responseType === 'stream') {
-          let response = '';
-          await new Promise(resolve => {
-            (translatedResponse?.data as Stream).on('data', chunk => {
-              response += chunk;
-            });
-            (translatedResponse?.data as Stream).on('end', resolve);
-          });
+          const response = [];
+
+          for await (const chunk of opts.data as Readable) {
+            response.push(chunk);
+          }
+
           translatedResponse.data = response as T;
         }
         throw new GaxiosError<T>(
@@ -172,21 +165,27 @@ export class Gaxios {
   }
 
   private async getResponseData(
-    opts: GaxiosOptions,
-    res: FetchResponse
+    opts: GaxiosOptionsPrepared,
+    res: Response
   ): Promise<any> {
+    if (
+      opts.maxContentLength &&
+      res.headers.has('content-length') &&
+      opts.maxContentLength <
+        Number.parseInt(res.headers?.get('content-length') || '')
+    ) {
+      throw new GaxiosError(
+        "Response's `Content-Length` is over the limit.",
+        opts,
+        Object.assign(res, {config: opts}) as GaxiosResponse
+      );
+    }
+
     switch (opts.responseType) {
       case 'stream':
         return res.body;
-      case 'json': {
-        let data = await res.text();
-        try {
-          data = JSON.parse(data);
-        } catch {
-          // continue
-        }
-        return data as {};
-      }
+      case 'json':
+        return res.json();
       case 'arraybuffer':
         return res.arrayBuffer();
       case 'blob':
@@ -200,7 +199,7 @@ export class Gaxios {
 
   #urlMayUseProxy(
     url: string | URL,
-    noProxy: GaxiosOptions['noProxy'] = []
+    noProxy: GaxiosOptionsPrepared['noProxy'] = []
   ): boolean {
     const candidate = new URL(url);
     const noProxyList = [...noProxy];
@@ -248,13 +247,13 @@ export class Gaxios {
    * Applies the request interceptors. The request interceptors are applied after the
    * call to prepareRequest is completed.
    *
-   * @param {GaxiosOptions} options The current set of options.
+   * @param {GaxiosOptionsPrepared} options The current set of options.
    *
-   * @returns {Promise<GaxiosOptions>} Promise that resolves to the set of options or response after interceptors are applied.
+   * @returns {Promise<GaxiosOptionsPrepared>} Promise that resolves to the set of options or response after interceptors are applied.
    */
   async #applyRequestInterceptors(
-    options: GaxiosOptions
-  ): Promise<GaxiosOptions> {
+    options: GaxiosOptionsPrepared
+  ): Promise<GaxiosOptionsPrepared> {
     let promiseChain = Promise.resolve(options);
 
     for (const interceptor of this.interceptors.request.values()) {
@@ -262,7 +261,7 @@ export class Gaxios {
         promiseChain = promiseChain.then(
           interceptor.resolved,
           interceptor.rejected
-        ) as Promise<GaxiosOptions>;
+        ) as Promise<GaxiosOptionsPrepared>;
       }
     }
 
@@ -273,9 +272,9 @@ export class Gaxios {
    * Applies the response interceptors. The response interceptors are applied after the
    * call to request is made.
    *
-   * @param {GaxiosOptions} options The current set of options.
+   * @param {GaxiosOptionsPrepared} options The current set of options.
    *
-   * @returns {Promise<GaxiosOptions>} Promise that resolves to the set of options or response after interceptors are applied.
+   * @returns {Promise<GaxiosOptionsPrepared>} Promise that resolves to the set of options or response after interceptors are applied.
    */
   async #applyResponseInterceptors(
     response: GaxiosResponse | Promise<GaxiosResponse>
@@ -300,7 +299,9 @@ export class Gaxios {
    * @param options The original options passed from the client.
    * @returns Prepared options, ready to make a request
    */
-  async #prepareRequest(options: GaxiosOptions): Promise<GaxiosOptions> {
+  async #prepareRequest(
+    options: GaxiosOptions
+  ): Promise<GaxiosOptionsPrepared> {
     const opts = extend(true, {}, this.defaults, options);
     if (!opts.url) {
       throw new Error('URL is required.');
@@ -312,14 +313,27 @@ export class Gaxios {
       opts.url = baseUrl.toString() + opts.url;
     }
 
-    opts.paramsSerializer = opts.paramsSerializer || this.paramsSerializer;
-    if (opts.params && Object.keys(opts.params).length > 0) {
-      let additionalQueryParams = opts.paramsSerializer(opts.params);
-      if (additionalQueryParams.startsWith('?')) {
-        additionalQueryParams = additionalQueryParams.slice(1);
+    // don't modify the properties of a default or provided URL
+    opts.url = new URL(opts.url);
+
+    if (opts.params) {
+      if (opts.paramsSerializer) {
+        let additionalQueryParams = opts.paramsSerializer(opts.params);
+
+        if (additionalQueryParams.startsWith('?')) {
+          additionalQueryParams = additionalQueryParams.slice(1);
+        }
+        const prefix = opts.url.toString().includes('?') ? '&' : '?';
+        opts.url = opts.url + prefix + additionalQueryParams;
+      } else {
+        const url = opts.url instanceof URL ? opts.url : new URL(opts.url);
+
+        for (const [key, value] of new URLSearchParams(opts.params)) {
+          url.searchParams.append(key, value);
+        }
+
+        opts.url = url;
       }
-      const prefix = opts.url.toString().includes('?') ? '&' : '?';
-      opts.url = opts.url + prefix + additionalQueryParams;
     }
 
     if (typeof options.maxContentLength === 'number') {
@@ -330,61 +344,66 @@ export class Gaxios {
       opts.follow = options.maxRedirects;
     }
 
-    opts.headers = opts.headers || {};
-    if (opts.multipart === undefined && opts.data) {
-      const isFormData =
-        typeof FormData === 'undefined'
-          ? false
-          : opts?.data instanceof FormData;
-      if (isStream.readable(opts.data)) {
-        opts.body = opts.data;
-      } else if (hasBuffer() && Buffer.isBuffer(opts.data)) {
-        // Do not attempt to JSON.stringify() a Buffer:
-        opts.body = opts.data;
-        if (!hasHeader(opts, 'Content-Type')) {
-          opts.headers['Content-Type'] = 'application/json';
-        }
-      } else if (typeof opts.data === 'object') {
+    const preparedHeaders =
+      opts.headers instanceof Headers
+        ? opts.headers
+        : new Headers(opts.headers);
+
+    const shouldDirectlyPassData =
+      typeof opts.data === 'string' ||
+      opts.data instanceof ArrayBuffer ||
+      opts.data instanceof Blob ||
+      opts.data instanceof File ||
+      opts.data instanceof FormData ||
+      opts.data instanceof Readable ||
+      opts.data instanceof ReadableStream ||
+      opts.data instanceof String ||
+      opts.data instanceof URLSearchParams ||
+      ArrayBuffer.isView(opts.data) || // `Buffer` (Node.js), `DataView`, `TypedArray`
+      /**
+       * @deprecated `node-fetch` or another third-party's request types
+       */
+      ['Blob', 'File', 'FormData'].includes(opts.data?.constructor?.name || '');
+
+    if (opts.multipart?.length) {
+      const boundary = await randomUUID();
+
+      preparedHeaders.set(
+        'content-type',
+        `multipart/related; boundary=${boundary}`
+      );
+
+      opts.body = Readable.from(
+        this.getMultipartRequest(opts.multipart, boundary)
+      ) as {} as ReadableStream;
+    } else if (shouldDirectlyPassData) {
+      opts.body = opts.data as BodyInit;
+    } else if (typeof opts.data === 'object') {
+      if (
+        preparedHeaders.get('Content-Type') ===
+        'application/x-www-form-urlencoded'
+      ) {
         // If www-form-urlencoded content type has been set, but data is
-        // provided as an object, serialize the content using querystring:
-        if (!isFormData) {
-          if (
-            getHeader(opts, 'content-type') ===
-            'application/x-www-form-urlencoded'
-          ) {
-            opts.body = opts.paramsSerializer(opts.data);
-          } else {
-            // } else if (!(opts.data instanceof FormData)) {
-            if (!hasHeader(opts, 'Content-Type')) {
-              opts.headers['Content-Type'] = 'application/json';
-            }
-            opts.body = JSON.stringify(opts.data);
-          }
-        }
+        // provided as an object, serialize the content
+        opts.body = opts.paramsSerializer
+          ? opts.paramsSerializer(opts.data as {})
+          : new URLSearchParams(opts.data as {});
       } else {
-        opts.body = opts.data;
+        if (!preparedHeaders.has('content-type')) {
+          preparedHeaders.set('content-type', 'application/json');
+        }
+
+        opts.body = JSON.stringify(opts.data);
       }
-    } else if (opts.multipart && opts.multipart.length > 0) {
-      // note: once the minimum version reaches Node 16,
-      // this can be replaced with randomUUID() function from crypto
-      // and the dependency on UUID removed
-      const boundary = v4();
-      opts.headers['Content-Type'] = `multipart/related; boundary=${boundary}`;
-      const bodyStream = new PassThrough();
-      opts.body = bodyStream;
-      pipeline(
-        this.getMultipartRequest(opts.multipart, boundary),
-        bodyStream,
-        () => {}
-      );
+    } else if (opts.data) {
+      opts.body = opts.data as BodyInit;
     }
 
     opts.validateStatus = opts.validateStatus || this.validateStatus;
     opts.responseType = opts.responseType || 'unknown';
-    if (!opts.headers['Accept'] && opts.responseType === 'json') {
-      opts.headers['Accept'] = 'application/json';
+    if (!preparedHeaders.has('accept') && opts.responseType === 'json') {
+      preparedHeaders.set('accept', 'application/json');
     }
-    opts.method = opts.method || 'GET';
 
     const proxy =
       opts.proxy ||
@@ -392,11 +411,10 @@ export class Gaxios {
       process?.env?.https_proxy ||
       process?.env?.HTTP_PROXY ||
       process?.env?.http_proxy;
-    const urlMayUseProxy = this.#urlMayUseProxy(opts.url, opts.noProxy);
 
     if (opts.agent) {
       // don't do any of the following options - use the user-provided agent.
-    } else if (proxy && urlMayUseProxy) {
+    } else if (proxy && this.#urlMayUseProxy(opts.url, opts.noProxy)) {
       const HttpsProxyAgent = await Gaxios.#getProxyAgent();
 
       if (this.agentCache.has(proxy)) {
@@ -429,7 +447,19 @@ export class Gaxios {
       opts.errorRedactor = defaultErrorRedactor;
     }
 
-    return opts;
+    if (opts.body && !('duplex' in opts)) {
+      /**
+       * required for Node.js and the type isn't available today
+       * @link https://github.com/nodejs/node/issues/46221
+       * @link https://github.com/microsoft/TypeScript-DOM-lib-generator/issues/1483
+       */
+      (opts as {duplex: string}).duplex = 'half';
+    }
+
+    return Object.assign(opts, {
+      headers: preparedHeaders,
+      url: opts.url instanceof URL ? opts.url : new URL(opts.url),
+    });
   }
 
   /**
@@ -440,46 +470,13 @@ export class Gaxios {
     return status >= 200 && status < 300;
   }
 
-  /**
-   * Encode a set of key/value pars into a querystring format (?foo=bar&baz=boo)
-   * @param params key value pars to encode
-   */
-  private paramsSerializer(params: {[index: string]: string | number}) {
-    return qs.stringify(params);
-  }
-
-  private translateResponse<T>(
-    opts: GaxiosOptions,
-    res: FetchResponse,
-    data?: T
-  ): GaxiosResponse<T> {
-    // headers need to be converted from a map to an obj
-    const headers = {} as Headers;
-    res.headers.forEach((value, key) => {
-      headers[key] = value;
-    });
-
-    return {
-      config: opts,
-      data: data as T,
-      headers,
-      status: res.status,
-      statusText: res.statusText,
-
-      // XMLHttpRequestLike
-      request: {
-        responseURL: res.url,
-      },
-    };
-  }
-
   /**
    * Attempts to parse a response by looking at the Content-Type header.
-   * @param {FetchResponse} response the HTTP response.
+   * @param {Response} response the HTTP response.
    * @returns {Promise<any>} a promise that resolves to the response data.
    */
   private async getResponseDataFromContentType(
-    response: FetchResponse
+    response: Response
   ): Promise<any> {
     let contentType = response.headers.get('Content-Type');
     if (contentType === null) {
@@ -517,8 +514,12 @@ export class Gaxios {
   ) {
     const finale = `--${boundary}--`;
     for (const currentPart of multipartOptions) {
+      const headers =
+        currentPart.headers instanceof Headers
+          ? currentPart.headers
+          : new Headers(currentPart.headers);
       const partContentType =
-        currentPart.headers['Content-Type'] || 'application/octet-stream';
+        headers.get('Content-Type') || 'application/octet-stream';
       const preamble = `--${boundary}\r\nContent-Type: ${partContentType}\r\n\r\n`;
       yield preamble;
       if (typeof currentPart.content === 'string') {
@@ -539,6 +540,14 @@ export class Gaxios {
   // using `import` to dynamically import the types here
   static #proxyAgent?: typeof import('https-proxy-agent').HttpsProxyAgent;
 
+  /**
+   * A cache for the lazily-loaded fetch library.
+   *
+   * Should use {@link Gaxios[#getFetch]} to retrieve.
+   */
+  //
+  static #fetch?: typeof nodeFetch | typeof fetch;
+
   /**
    * Imports, caches, and returns a proxy agent - if not already imported
    *
@@ -549,4 +558,14 @@ export class Gaxios {
 
     return this.#proxyAgent;
   }
+
+  static async #getFetch() {
+    const hasWindow = typeof window !== 'undefined' && !!window;
+
+    this.#fetch ||= hasWindow
+      ? window.fetch
+      : (await import('node-fetch')).default;
+
+    return this.#fetch;
+  }
 }
diff --git a/src/index.ts b/src/index.ts
index a18ddef3..c563eac6 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -18,7 +18,7 @@ export {
   GaxiosError,
   GaxiosPromise,
   GaxiosResponse,
-  Headers,
+  GaxiosOptionsPrepared,
   RetryConfig,
 } from './common';
 export {Gaxios, GaxiosOptions};
diff --git a/src/interceptor.ts b/src/interceptor.ts
index d52aacbb..9ccfad86 100644
--- a/src/interceptor.ts
+++ b/src/interceptor.ts
@@ -11,12 +11,14 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-import {GaxiosError, GaxiosOptions, GaxiosResponse} from './common';
+import {GaxiosError, GaxiosOptionsPrepared, GaxiosResponse} from './common';
 
 /**
  * Interceptors that can be run for requests or responses. These interceptors run asynchronously.
  */
-export interface GaxiosInterceptor<T extends GaxiosOptions | GaxiosResponse> {
+export interface GaxiosInterceptor<
+  T extends GaxiosOptionsPrepared | GaxiosResponse,
+> {
   /**
    * Function to be run when applying an interceptor.
    *
@@ -37,5 +39,5 @@ export interface GaxiosInterceptor<T extends GaxiosOptions | GaxiosResponse> {
  * Class to manage collections of GaxiosInterceptors for both requests and responses.
  */
 export class GaxiosInterceptorManager<
-  T extends GaxiosOptions | GaxiosResponse,
+  T extends GaxiosOptionsPrepared | GaxiosResponse,
 > extends Set<GaxiosInterceptor<T> | null> {}
diff --git a/src/retry.ts b/src/retry.ts
index 4f28f943..6f696676 100644
--- a/src/retry.ts
+++ b/src/retry.ts
@@ -75,7 +75,7 @@ export async function getRetryConfig(err: GaxiosError) {
 
   const delay = getNextRetryDelay(config);
 
-  // We're going to retry!  Incremenent the counter.
+  // We're going to retry!  Increment the counter.
   err.config.retryConfig!.currentRetryAttempt! += 1;
 
   // Create a promise that invokes the retry after the backOffDelay
@@ -102,9 +102,11 @@ export async function getRetryConfig(err: GaxiosError) {
 function shouldRetryRequest(err: GaxiosError) {
   const config = getConfig(err);
 
-  // node-fetch raises an AbortError if signaled:
-  // https://github.com/bitinn/node-fetch#request-cancellation-with-abortsignal
-  if (err.name === 'AbortError' || err.error?.name === 'AbortError') {
+  if (
+    err.config.signal?.aborted ||
+    err.name === 'AbortError' ||
+    err.error?.name === 'AbortError'
+  ) {
     return false;
   }
 
@@ -123,8 +125,10 @@ function shouldRetryRequest(err: GaxiosError) {
 
   // Only retry with configured HttpMethods.
   if (
-    !err.config.method ||
-    config.httpMethodsToRetry!.indexOf(err.config.method.toUpperCase()) < 0
+    !config.httpMethodsToRetry ||
+    !config.httpMethodsToRetry.includes(
+      err.config.method?.toUpperCase() || 'GET'
+    )
   ) {
     return false;
   }
diff --git a/system-test/fixtures/sample/webpack.config.js b/system-test/fixtures/sample/webpack.config.js
index 1a65d5a4..f83630cc 100644
--- a/system-test/fixtures/sample/webpack.config.js
+++ b/system-test/fixtures/sample/webpack.config.js
@@ -32,7 +32,6 @@ module.exports = {
       buffer: 'browserify',
       process: false,
       os: false,
-      querystring: false,
       path: false,
       stream: 'stream-browserify',
       url: false,
diff --git a/test/test.getch.ts b/test/test.getch.ts
index 26a63bbd..40416677 100644
--- a/test/test.getch.ts
+++ b/test/test.getch.ts
@@ -16,7 +16,6 @@ import nock from 'nock';
 import sinon from 'sinon';
 import stream, {Readable} from 'stream';
 import {describe, it, afterEach} from 'mocha';
-import fetch from 'node-fetch';
 import {HttpsProxyAgent} from 'https-proxy-agent';
 import {
   Gaxios,
@@ -26,12 +25,9 @@ import {
   GaxiosResponse,
   GaxiosPromise,
 } from '../src';
-import {GAXIOS_ERROR_SYMBOL, Headers} from '../src/common';
+import {GAXIOS_ERROR_SYMBOL, GaxiosOptionsPrepared} from '../src/common';
 import {pkg} from '../src/util';
-import qs from 'querystring';
 import fs from 'fs';
-import {Blob} from 'node-fetch';
-global.FormData = require('form-data');
 
 nock.disableNetConnect();
 
@@ -107,7 +103,7 @@ describe('🚙 error handling', () => {
 
   it('should not throw an error during a translation error', () => {
     const notJSON = '.';
-    const response: GaxiosResponse = {
+    const response = {
       config: {
         responseType: 'json',
       },
@@ -115,14 +111,17 @@ describe('🚙 error handling', () => {
       status: 500,
       statusText: '',
       headers: {},
-      request: {
-        responseURL: url,
-      },
-    };
-
-    const error = new GaxiosError('translation test', {}, response);
+      // workaround for `node-fetch`'s `.data` deprecation...
+      bodyUsed: true,
+    } as GaxiosResponse;
+
+    const error = new GaxiosError(
+      'translation test',
+      {} as GaxiosOptionsPrepared,
+      response
+    );
 
-    assert(error.response, undefined);
+    assert(error.response);
     assert.equal(error.response.data, notJSON);
   });
 
@@ -131,7 +130,7 @@ describe('🚙 error handling', () => {
 
     const wrongVersion = {[GAXIOS_ERROR_SYMBOL]: '0.0.0'};
     const correctVersion = {[GAXIOS_ERROR_SYMBOL]: pkg.version};
-    const child = new A('', {});
+    const child = new A('', {} as GaxiosOptionsPrepared);
 
     assert.equal(wrongVersion instanceof GaxiosError, false);
     assert.equal(correctVersion instanceof GaxiosError, true);
@@ -140,11 +139,18 @@ describe('🚙 error handling', () => {
 });
 
 describe('🥁 configuration options', () => {
-  it('should accept URL objects', async () => {
+  it('should accept `URL` objects', async () => {
     const scope = nock(url).get('/').reply(204);
     const res = await request({url: new URL(url)});
     scope.done();
-    assert.strictEqual(res.config.method, 'GET');
+    assert.strictEqual(res.status, 204);
+  });
+
+  it('should accept `Request` objects', async () => {
+    const scope = nock(url).get('/').reply(204);
+    const res = await request(new Request(url));
+    scope.done();
+    assert.strictEqual(res.status, 204);
   });
 
   it('should use options passed into the constructor', async () => {
@@ -160,8 +166,8 @@ describe('🥁 configuration options', () => {
     const inst = new Gaxios({headers: {apple: 'juice'}});
     const res = await inst.request({url, headers: {figgy: 'pudding'}});
     scope.done();
-    assert.strictEqual(res.config.headers!.apple, 'juice');
-    assert.strictEqual(res.config.headers!.figgy, 'pudding');
+    assert.strictEqual(res.config.headers.get('apple'), 'juice');
+    assert.strictEqual(res.config.headers.get('figgy'), 'pudding');
   });
 
   it('should allow setting a base url in the options', async () => {
@@ -181,9 +187,14 @@ describe('🥁 configuration options', () => {
 
   it('should allow setting maxContentLength', async () => {
     const body = {hello: '🌎'};
-    const scope = nock(url).get('/').reply(200, body);
+    const scope = nock(url)
+      .get('/')
+      .reply(200, body, {'content-length': body.toString().length.toString()});
     const maxContentLength = 1;
-    await assert.rejects(request({url, maxContentLength}), /over limit/);
+    await assert.rejects(request({url, maxContentLength}), (err: Error) => {
+      return err instanceof GaxiosError && /limit/.test(err.message);
+    });
+
     scope.done();
   });
 
@@ -196,27 +207,17 @@ describe('🥁 configuration options', () => {
     const res = await request({url});
     scopes.forEach(x => x.done());
     assert.deepStrictEqual(res.data, body);
-    assert.strictEqual(res.request.responseURL, `${url}/foo`);
-  });
-
-  it('should support disabling redirects', async () => {
-    const scope = nock(url).get('/').reply(302, undefined, {location: '/foo'});
-    const maxRedirects = 0;
-    await assert.rejects(request({url, maxRedirects}), /maximum redirect/);
-    scope.done();
+    assert.strictEqual(res.url, `${url}/foo`);
   });
 
   it('should allow overriding the adapter', async () => {
-    const response: GaxiosResponse = {
+    const response = {
       data: {hello: '🌎'},
       config: {},
       status: 200,
       statusText: 'OK',
-      headers: {},
-      request: {
-        responseURL: url,
-      },
-    };
+      headers: new Headers(),
+    } as GaxiosResponse;
     const adapter = () => Promise.resolve(response);
     const res = await request({url, adapter});
     assert.strictEqual(response, res);
@@ -256,7 +257,7 @@ describe('🥁 configuration options', () => {
     const scope = nock(url).get(path).reply(200, {});
     const res = await request(opts);
     assert.strictEqual(res.status, 200);
-    assert.strictEqual(res.config.url, url + path);
+    assert.strictEqual(res.config.url?.toString(), url + path);
     scope.done();
   });
 
@@ -266,7 +267,7 @@ describe('🥁 configuration options', () => {
     const scope = nock(url).get(path).reply(200, {});
     const res = await request(opts);
     assert.strictEqual(res.status, 200);
-    assert.strictEqual(res.config.url, url + path);
+    assert.strictEqual(res.config.url?.toString(), url + path);
     scope.done();
   });
 
@@ -287,7 +288,10 @@ describe('🥁 configuration options', () => {
     const scope = nock(url).get(path).reply(200, {});
     const res = await request(opts);
     assert.strictEqual(res.status, 200);
-    assert.strictEqual(res.config.url, url + qs);
+    assert.strictEqual(
+      res.config.url?.toString(),
+      new URL(url + qs).toString()
+    );
     scope.done();
   });
 
@@ -300,7 +304,7 @@ describe('🥁 configuration options', () => {
     const scope = nock(url).get(path).reply(200, {});
     const res = await request(opts);
     assert.strictEqual(res.status, 200);
-    assert.strictEqual(res.config.url, url + path);
+    assert.strictEqual(res.config.url?.toString(), url + path);
     scope.done();
   });
 
@@ -318,7 +322,7 @@ describe('🥁 configuration options', () => {
     const scope = nock(url).get(`/${qs}`).reply(200, {});
     const res = await request(opts);
     assert.strictEqual(res.status, 200);
-    assert.strictEqual(res.config.url, url + qs);
+    assert.strictEqual(res.config.url.toString(), new URL(url + qs).toString());
     scope.done();
   });
 
@@ -606,8 +610,30 @@ describe('🥁 configuration options', () => {
   it('should not stringify the data if it is appended by a form', async () => {
     const formData = new FormData();
     formData.append('test', '123');
-    // I don't think matching formdata is supported in nock, so skipping: https://github.com/nock/nock/issues/887
-    const scope = nock(url).post('/').reply(200);
+
+    const scope = nock(url)
+      .post('/', body => {
+        /**
+         * Sample from native `node-fetch`
+         * body: '------3785545705014550845559551617\r\n' +
+         * 'Content-Disposition: form-data; name="test"\r\n' +
+         * '\r\n' +
+         * '123\r\n' +
+         * '------3785545705014550845559551617--',
+         */
+
+        /**
+         * Sample from native `fetch`
+         * body: '------formdata-undici-0.39470493152687736\r\n' +
+         * 'Content-Disposition: form-data; name="test"\r\n' +
+         * '\r\n' +
+         * '123\r\n' +
+         * '------formdata-undici-0.39470493152687736--',
+         */
+
+        return body.match('Content-Disposition: form-data;');
+      })
+      .reply(200);
     const res = await request({
       url,
       method: 'POST',
@@ -615,15 +641,28 @@ describe('🥁 configuration options', () => {
     });
     scope.done();
     assert.deepStrictEqual(res.config.data, formData);
+    assert.ok(res.config.body instanceof FormData);
     assert.ok(res.config.data instanceof FormData);
-    assert.deepEqual(res.config.body, undefined);
   });
 
-  it('should allow explicitly setting the fetch implementation to node-fetch', async () => {
-    const scope = nock(url).get('/').reply(200);
-    const res = await request({url, fetchImplementation: fetch});
+  it('should allow explicitly setting the fetch implementation', async () => {
+    let customFetchCalled = false;
+    const myFetch = (...args: Parameters<typeof fetch>) => {
+      customFetchCalled = true;
+      return fetch(...args);
+    };
+
+    const scope = nock(url).post('/').reply(204);
+    const res = await request({
+      url,
+      method: 'POST',
+      fetchImplementation: myFetch,
+      // This `data` ensures the 'duplex' option has been set
+      data: {sample: 'data'},
+    });
+    assert(customFetchCalled);
+    assert.equal(res.status, 204);
     scope.done();
-    assert.deepStrictEqual(res.status, 200);
   });
 
   it('should be able to disable the `errorRedactor`', async () => {
@@ -666,10 +705,10 @@ describe('🎏 data handling', () => {
 
   it('should accept a string in the request data', async () => {
     const body = {hello: '🌎'};
-    const encoded = qs.stringify(body);
+    const encoded = new URLSearchParams(body);
     const scope = nock(url)
       .matchHeader('content-type', 'application/x-www-form-urlencoded')
-      .post('/', encoded)
+      .post('/', encoded.toString())
       .reply(200, {});
     const res = await request({
       url,
@@ -718,7 +757,7 @@ describe('🎏 data handling', () => {
     const body = {hello: '🌎'};
     const scope = nock(url)
       .matchHeader('Content-Type', 'application/x-www-form-urlencoded')
-      .post('/', qs.stringify(body))
+      .post('/', new URLSearchParams(body).toString())
       .reply(200, {});
     const res = await request({
       url,
@@ -740,6 +779,18 @@ describe('🎏 data handling', () => {
     assert(res.data instanceof stream.Readable);
   });
 
+  it('should return a `ReadableStream` when `fetch` has been provided ', async () => {
+    const body = {hello: '🌎'};
+    const scope = nock(url).get('/').reply(200, body);
+    const res = await request<ReadableStream>({
+      url,
+      responseType: 'stream',
+      fetchImplementation: fetch,
+    });
+    scope.done();
+    assert(res.data instanceof ReadableStream);
+  });
+
   it('should return an ArrayBuffer if asked nicely', async () => {
     const body = {hello: '🌎'};
     const scope = nock(url).get('/').reply(200, body);
@@ -777,7 +828,10 @@ describe('🎏 data handling', () => {
     const res = await request({url});
     scope.done();
     assert.ok(res.data);
-    assert.strictEqual(res.statusText, 'OK');
+    // node-fetch and native fetch specs differ...
+    // https://github.com/node-fetch/node-fetch/issues/1066
+    assert.strictEqual(typeof res.statusText, 'string');
+    // assert.strictEqual(res.statusText, 'OK');
   });
 
   it('should return JSON when response Content-Type=application/json', async () => {
@@ -907,7 +961,7 @@ describe('🎏 data handling', () => {
     customURL.searchParams.append('client_secret', 'data');
     customURL.searchParams.append('random', 'non-sensitive');
 
-    const config: GaxiosOptions = {
+    const config = {
       headers: {
         Authentication: 'My Auth',
         /**
@@ -924,7 +978,7 @@ describe('🎏 data handling', () => {
         client_secret: 'data',
       },
       body: 'grant_type=somesensitivedata&assertion=somesensitivedata&client_secret=data',
-    };
+    } as const;
 
     // simulate JSON response
     const responseHeaders = {
@@ -958,12 +1012,16 @@ describe('🎏 data handling', () => {
       assert.notStrictEqual(e.config, config);
 
       // config redactions - headers
-      assert(e.config.headers);
-      assert.deepStrictEqual(e.config.headers, {
+      const expectedRequestHeaders = new Headers({
         ...config.headers, // non-redactables should be present
         Authentication: REDACT,
         AUTHORIZATION: REDACT,
       });
+      const actualHeaders = e.config.headers;
+
+      expectedRequestHeaders.forEach((value, key) => {
+        assert.equal(actualHeaders.get(key), value);
+      });
 
       // config redactions - data
       assert.deepStrictEqual(e.config.data, {
@@ -973,8 +1031,19 @@ describe('🎏 data handling', () => {
         client_secret: REDACT,
       });
 
-      // config redactions - body
-      assert.deepStrictEqual(e.config.body, REDACT);
+      assert.deepStrictEqual(
+        Object.fromEntries(e.config.body as URLSearchParams),
+        {
+          ...config.data, // non-redactables should be present
+          grant_type: REDACT,
+          assertion: REDACT,
+          client_secret: REDACT,
+        }
+      );
+
+      expectedRequestHeaders.forEach((value, key) => {
+        assert.equal(actualHeaders.get(key), value);
+      });
 
       // config redactions - url
       assert(e.config.url);
@@ -988,16 +1057,17 @@ describe('🎏 data handling', () => {
       assert(e.response);
       assert.deepStrictEqual(e.response.config, e.config);
 
-      const expectedHeaders: Headers = {
+      const expectedResponseHeaders = new Headers({
         ...responseHeaders, // non-redactables should be present
-        authentication: REDACT,
-        authorization: REDACT,
-      };
+      });
 
-      delete expectedHeaders['AUTHORIZATION'];
-      delete expectedHeaders['Authentication'];
+      expectedResponseHeaders.set('authentication', REDACT);
+      expectedResponseHeaders.set('authorization', REDACT);
+
+      expectedResponseHeaders.forEach((value, key) => {
+        assert.equal(e.response?.headers.get(key), value);
+      });
 
-      assert.deepStrictEqual(e.response.headers, expectedHeaders);
       assert.deepStrictEqual(e.response.data, {
         ...response, // non-redactables should be present
         assertion: REDACT,
@@ -1042,22 +1112,6 @@ describe('🍂 defaults & instances', () => {
     assert.deepStrictEqual(res.data, {});
   });
 
-  it('should set content-type to application/json by default, for buffer', async () => {
-    const pkg = fs.readFileSync('./package.json');
-    const pkgJson = JSON.parse(pkg.toString('utf8'));
-    const scope = nock(url)
-      .matchHeader('content-type', 'application/json')
-      .post('/', pkgJson)
-      .reply(200, {});
-    const res = await request({
-      url,
-      method: 'POST',
-      data: pkg,
-    });
-    scope.done();
-    assert.deepStrictEqual(res.data, {});
-  });
-
   describe('mtls', () => {
     class GaxiosAssertAgentCache extends Gaxios {
       getAgentCache() {
@@ -1065,7 +1119,7 @@ describe('🍂 defaults & instances', () => {
       }
       // eslint-disable-next-line @typescript-eslint/no-explicit-any
       protected async _request<T = any>(
-        opts: GaxiosOptions = {}
+        opts: GaxiosOptionsPrepared
       ): GaxiosPromise<T> {
         assert(opts.agent);
         return super._request(opts);
@@ -1081,8 +1135,8 @@ describe('🍂 defaults & instances', () => {
       });
       const res = await inst.request({url, headers: {figgy: 'pudding'}});
       scope.done();
-      assert.strictEqual(res.config.headers!.apple, 'juice');
-      assert.strictEqual(res.config.headers!.figgy, 'pudding');
+      assert.strictEqual(res.config.headers.get('apple'), 'juice');
+      assert.strictEqual(res.config.headers.get('figgy'), 'pudding');
       const agentCache = inst.getAgentCache();
       assert(agentCache.get(key));
     });
@@ -1113,7 +1167,7 @@ describe('interceptors', () => {
       const instance = new Gaxios();
       instance.interceptors.request.add({
         resolved: config => {
-          config.headers = {hello: 'world'};
+          config.headers.set('hello', 'world');
           return Promise.resolve(config);
         },
       });
@@ -1130,7 +1184,7 @@ describe('interceptors', () => {
             validateStatus: () => {
               return true;
             },
-          }) as unknown as Promise<GaxiosOptions>
+          }) as unknown as Promise<GaxiosOptionsPrepared>
       );
       const instance = new Gaxios();
       const interceptor = {resolved: spyFunc};
@@ -1152,22 +1206,22 @@ describe('interceptors', () => {
       const instance = new Gaxios();
       instance.interceptors.request.add({
         resolved: config => {
-          config.headers!['foo'] = 'bar';
+          config.headers.set('foo', 'bar');
           return Promise.resolve(config);
         },
       });
       instance.interceptors.request.add({
         resolved: config => {
-          assert.strictEqual(config.headers!['foo'], 'bar');
-          config.headers!['bar'] = 'baz';
+          assert.strictEqual(config.headers.get('foo'), 'bar');
+          config.headers.set('bar', 'baz');
           return Promise.resolve(config);
         },
       });
       instance.interceptors.request.add({
         resolved: config => {
-          assert.strictEqual(config.headers!['foo'], 'bar');
-          assert.strictEqual(config.headers!['bar'], 'baz');
-          config.headers!['baz'] = 'buzz';
+          assert.strictEqual(config.headers.get('foo'), 'bar');
+          assert.strictEqual(config.headers.get('bar'), 'baz');
+          config.headers.set('baz', 'buzz');
           return Promise.resolve(config);
         },
       });
@@ -1184,7 +1238,7 @@ describe('interceptors', () => {
             validateStatus: () => {
               return true;
             },
-          }) as unknown as Promise<GaxiosOptions>
+          }) as unknown as Promise<GaxiosOptionsPrepared>
       );
       const instance = new Gaxios();
       instance.interceptors.request.add({
@@ -1212,7 +1266,7 @@ describe('interceptors', () => {
       });
       instance.interceptors.request.add({
         resolved: config => {
-          config.headers = {hello: 'world'};
+          config.headers.set('hello', 'world');
           return Promise.resolve(config);
         },
         rejected: err => {
@@ -1230,13 +1284,13 @@ describe('interceptors', () => {
       const instance = new Gaxios();
       instance.interceptors.response.add({
         resolved(response) {
-          response.headers['hello'] = 'world';
+          response.headers.set('hello', 'world');
           return Promise.resolve(response);
         },
       });
       const resp = await instance.request({url});
       scope.done();
-      assert.strictEqual(resp.headers['hello'], 'world');
+      assert.strictEqual(resp.headers.get('hello'), 'world');
     });
 
     it('should not invoke a response interceptor after it is removed', async () => {
@@ -1265,30 +1319,30 @@ describe('interceptors', () => {
       const instance = new Gaxios();
       instance.interceptors.response.add({
         resolved: response => {
-          response.headers!['foo'] = 'bar';
+          response.headers.set('foo', 'bar');
           return Promise.resolve(response);
         },
       });
       instance.interceptors.response.add({
         resolved: response => {
-          assert.strictEqual(response.headers!['foo'], 'bar');
-          response.headers!['bar'] = 'baz';
+          assert.strictEqual(response.headers.get('foo'), 'bar');
+          response.headers.set('bar', 'baz');
           return Promise.resolve(response);
         },
       });
       instance.interceptors.response.add({
         resolved: response => {
-          assert.strictEqual(response.headers!['foo'], 'bar');
-          assert.strictEqual(response.headers!['bar'], 'baz');
-          response.headers!['baz'] = 'buzz';
+          assert.strictEqual(response.headers.get('foo'), 'bar');
+          assert.strictEqual(response.headers.get('bar'), 'baz');
+          response.headers.set('baz', 'buzz');
           return Promise.resolve(response);
         },
       });
       const resp = await instance.request({url, headers: {}});
       scope.done();
-      assert.strictEqual(resp.headers['foo'], 'bar');
-      assert.strictEqual(resp.headers['bar'], 'baz');
-      assert.strictEqual(resp.headers['baz'], 'buzz');
+      assert.strictEqual(resp.headers.get('foo'), 'bar');
+      assert.strictEqual(resp.headers.get('bar'), 'baz');
+      assert.strictEqual(resp.headers.get('baz'), 'buzz');
     });
 
     it('should not invoke a any response interceptors after they are removed', async () => {
diff --git a/test/test.retry.ts b/test/test.retry.ts
index 7412da5f..00ecbe16 100644
--- a/test/test.retry.ts
+++ b/test/test.retry.ts
@@ -11,7 +11,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-import {AbortController} from 'abort-controller';
 import assert from 'assert';
 import nock from 'nock';
 import {describe, it, afterEach} from 'mocha';
@@ -249,7 +248,7 @@ describe('🛸 retry & exponential backoff', () => {
   it('should retry on ENOTFOUND', async () => {
     const body = {spicy: '🌮'};
     const scopes = [
-      nock(url).get('/').replyWithError({code: 'ENOTFOUND'}),
+      nock(url).get('/').reply(500, {code: 'ENOTFOUND'}),
       nock(url).get('/').reply(200, body),
     ];
     const res = await request({url, retry: true});
@@ -260,7 +259,7 @@ describe('🛸 retry & exponential backoff', () => {
   it('should retry on ETIMEDOUT', async () => {
     const body = {sizzling: '🥓'};
     const scopes = [
-      nock(url).get('/').replyWithError({code: 'ETIMEDOUT'}),
+      nock(url).get('/').reply(500, {code: 'ETIMEDOUT'}),
       nock(url).get('/').reply(200, body),
     ];
     const res = await request({url, retry: true});
@@ -269,13 +268,14 @@ describe('🛸 retry & exponential backoff', () => {
   });
 
   it('should allow configuring noResponseRetries', async () => {
-    const scope = nock(url).get('/').replyWithError({code: 'ETIMEDOUT'});
+    // `nock` is not listening, therefore it should fail
     const config = {url, retryConfig: {noResponseRetries: 0}};
-    await assert.rejects(request(config), (e: Error) => {
-      const cfg = getConfig(e);
-      return cfg!.currentRetryAttempt === 0;
+    await assert.rejects(request(config), (e: GaxiosError) => {
+      return (
+        e.code === 'ENETUNREACH' &&
+        e.config.retryConfig?.currentRetryAttempt === 0
+      );
     });
-    scope.done();
   });
 
   it('should delay the initial retry by 100ms by default', async () => {
diff --git a/tsconfig.json b/tsconfig.json
index dac05e8b..e10edbe0 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,10 +1,12 @@
 {
   "extends": "./node_modules/gts/tsconfig-google.json",
   "compilerOptions": {
-    "lib": ["es2015", "dom"],
+    "lib": ["es2020", "dom"],
     "rootDir": ".",
     "outDir": "build",
-    "esModuleInterop": true
+    "esModuleInterop": true,
+    "module": "Node16",
+    "moduleResolution": "Node16",
   },
   "include": [
     "src/*.ts",
diff --git a/webpack-tests.config.js b/webpack-tests.config.js
index 2590ab03..e29599a2 100644
--- a/webpack-tests.config.js
+++ b/webpack-tests.config.js
@@ -32,7 +32,6 @@ module.exports = {
       buffer: 'browserify',
       process: false,
       os: false,
-      querystring: false,
       path: false,
       stream: 'stream-browserify',
       url: false,
diff --git a/webpack.config.js b/webpack.config.js
index bbb1b492..0621b6dd 100644
--- a/webpack.config.js
+++ b/webpack.config.js
@@ -32,7 +32,6 @@ module.exports = {
       buffer: 'browserify',
       process: false,
       os: false,
-      querystring: false,
       path: false,
       stream: 'stream-browserify',
       url: false,