diff --git a/src/constants.ts b/src/constants.ts
index 14c4944e..b28a3da5 100644
--- a/src/constants.ts
+++ b/src/constants.ts
@@ -1,10 +1,11 @@
 // OpenSauced constants
 export const OPEN_SAUCED_INSIGHTS_DOMAIN = import.meta.env.VITE_OPEN_SAUCED_INSIGHTS_DOMAIN;
 export const OPEN_SAUCED_API_ENDPOINT = import.meta.env.VITE_OPEN_SAUCED_API_ENDPOINT;
-export const SUPABASE_LOGIN_URL = `https://${import.meta.env.VITE_OPEN_SAUCED_SUPABASE_ID}.supabase.co/auth/v1/authorize?provider=github&redirect_to=https://${OPEN_SAUCED_INSIGHTS_DOMAIN}/`;
+export const SUPABASE_LOGIN_URL = `https://${import.meta.env.VITE_OPEN_SAUCED_SUPABASE_ID}.supabase.co/auth/v1/authorize`;
 
 
 export const SUPABASE_AUTH_COOKIE_NAME = `sb-${import.meta.env.VITE_OPEN_SAUCED_SUPABASE_ID}-auth-token`;
+export const SUPABASE_PKCE_VERIFIER_COOKIE_NAME = `sb-${import.meta.env.VITE_OPEN_SAUCED_SUPABASE_ID}-auth-token-code-verifier`;
 export const OPEN_SAUCED_AUTH_TOKEN_KEY = "os-access-token";
 export const OPEN_SAUCED_OPTED_LOG_OUT_KEY = "opted-log-out";
 export const AI_PR_DESCRIPTION_CONFIG_KEY = "ai-pr-description-config";
diff --git a/src/content-scripts/components/AICodeReview/AICodeReviewMenu.ts b/src/content-scripts/components/AICodeReview/AICodeReviewMenu.ts
index c5d76ddf..9c52ba7a 100644
--- a/src/content-scripts/components/AICodeReview/AICodeReviewMenu.ts
+++ b/src/content-scripts/components/AICodeReview/AICodeReviewMenu.ts
@@ -1,13 +1,10 @@
-import {
-    SUPABASE_LOGIN_URL,
-    GITHUB_PR_SUGGESTION_TEXT_AREA_SELECTOR,
-} from "../../../constants";
+import { GITHUB_PR_SUGGESTION_TEXT_AREA_SELECTOR } from "../../../constants";
 import { insertTextAtCursor } from "../../../utils/ai-utils/cursorPositionInsert";
 import {
     DescriptionConfig,
     getAIDescriptionConfig,
 } from "../../../utils/ai-utils/descriptionconfig";
-import { getAuthToken, isLoggedIn } from "../../../utils/checkAuthentication";
+import { getAuthToken, isLoggedIn, optLogIn } from "../../../utils/checkAuthentication";
 import { createHtmlElement } from "../../../utils/createHtmlElement";
 import { isOutOfContextBounds } from "../../../utils/fetchGithubAPIData";
 
@@ -73,7 +70,7 @@ const handleSubmit = async (
 
     try {
         if (!(await isLoggedIn())) {
-            return window.open(SUPABASE_LOGIN_URL, "_blank");
+            return void optLogIn();
         }
 
         if (!logo || !button) {
diff --git a/src/content-scripts/components/GenerateAIDescription/DescriptionGeneratorButton.ts b/src/content-scripts/components/GenerateAIDescription/DescriptionGeneratorButton.ts
index f5374fca..e5dd01d5 100644
--- a/src/content-scripts/components/GenerateAIDescription/DescriptionGeneratorButton.ts
+++ b/src/content-scripts/components/GenerateAIDescription/DescriptionGeneratorButton.ts
@@ -3,10 +3,10 @@ import openSaucedLogoIcon from "../../../assets/opensauced-icon.svg";
 import { getPullRequestAPIURL } from "../../../utils/urlMatchers";
 import { getDescriptionContext, isOutOfContextBounds } from "../../../utils/fetchGithubAPIData";
 import { generateDescription } from "../../../utils/ai-utils/openai";
-import { GITHUB_PR_COMMENT_TEXT_AREA_SELECTOR, SUPABASE_LOGIN_URL } from "../../../constants";
+import { GITHUB_PR_COMMENT_TEXT_AREA_SELECTOR } from "../../../constants";
 import { insertTextAtCursor } from "../../../utils/ai-utils/cursorPositionInsert";
 import { getAIDescriptionConfig } from "../../../utils/ai-utils/descriptionconfig";
-import { getAuthToken, isLoggedIn } from "../../../utils/checkAuthentication";
+import { getAuthToken, isLoggedIn, optLogIn } from "../../../utils/checkAuthentication";
 
 export const DescriptionGeneratorButton = () => {
     const descriptionGeneratorButton = createHtmlElement("a", {
@@ -27,7 +27,7 @@ const handleSubmit = async () => {
 
     try {
         if (!(await isLoggedIn())) {
-            return window.open(SUPABASE_LOGIN_URL, "_blank");
+            return void optLogIn();
         }
 
         if (!logo || !button) {
diff --git a/src/utils/checkAuthentication.ts b/src/utils/checkAuthentication.ts
index 51741f80..89c42cf2 100644
--- a/src/utils/checkAuthentication.ts
+++ b/src/utils/checkAuthentication.ts
@@ -1,9 +1,9 @@
 import {
     OPEN_SAUCED_AUTH_TOKEN_KEY,
-    OPEN_SAUCED_OPTED_LOG_OUT_KEY, SUPABASE_LOGIN_URL,
+    OPEN_SAUCED_INSIGHTS_DOMAIN,
+    OPEN_SAUCED_OPTED_LOG_OUT_KEY, SUPABASE_LOGIN_URL, SUPABASE_PKCE_VERIFIER_COOKIE_NAME,
 } from "../constants";
 
-
 export const isLoggedIn = async (): Promise<boolean> => Object.entries(await chrome.storage.sync.get(OPEN_SAUCED_AUTH_TOKEN_KEY)).length !== 0;
 
 export const getAuthToken = async (): Promise<string> => (await chrome.storage.sync.get(OPEN_SAUCED_AUTH_TOKEN_KEY))[OPEN_SAUCED_AUTH_TOKEN_KEY];
@@ -13,14 +13,66 @@ export const optLogOut = () => {
     void chrome.storage.local.set({ [OPEN_SAUCED_OPTED_LOG_OUT_KEY]: true });
 };
 
-export const optLogIn = () => {
+export const optLogIn = async () => {
     if (typeof window === "undefined") {
         return;
     }
     void chrome.storage.local.set({ [OPEN_SAUCED_OPTED_LOG_OUT_KEY]: false });
-    window.open(SUPABASE_LOGIN_URL, "_blank");
+
+    const verifier = generatePKCEVerifier();
+    const challenge = await generatePKCEChallenge(verifier);
+
+    const loginURL = new URL(SUPABASE_LOGIN_URL);
+
+    loginURL.searchParams.append("provider", "github");
+    loginURL.searchParams.append(
+        "redirect_to",
+        `https://${OPEN_SAUCED_INSIGHTS_DOMAIN}`,
+    );
+    loginURL.searchParams.append("code_challenge_method", "s256");
+    loginURL.searchParams.append("code_challenge", challenge);
+
+    await chrome.cookies.set({
+        url: `https://${OPEN_SAUCED_INSIGHTS_DOMAIN}`,
+        name: SUPABASE_PKCE_VERIFIER_COOKIE_NAME,
+        value: verifier,
+    });
+    window.open(loginURL, "_blank");
 };
 
 export const hasOptedLogOut = async (): Promise<boolean> => (await chrome.storage.local.get(OPEN_SAUCED_OPTED_LOG_OUT_KEY))[OPEN_SAUCED_OPTED_LOG_OUT_KEY] === true;
 
 export const removeAuthTokenFromStorage = async (): Promise<void> => chrome.storage.sync.remove(OPEN_SAUCED_AUTH_TOKEN_KEY);
+
+// Custom browser only PKCE implementation based on https://github.com/supabase/gotrue-js
+
+const dec2hex = (dec: number) => (`0${dec.toString(16)}`).substring(-2);
+
+const generatePKCEVerifier = () => {
+    const verifierLength = 56;
+    const array = new Uint32Array(verifierLength);
+
+    crypto.getRandomValues(array);
+    return Array.from(array, dec2hex).join("");
+};
+
+const sha256 = async (randomString: string) => {
+    const encoder = (new TextEncoder);
+    const encodedData = encoder.encode(randomString);
+    const hash = await window.crypto.subtle.digest("SHA-256", encodedData);
+    const bytes = new Uint8Array(hash);
+
+    return Array.from(bytes)
+        .map(c => String.fromCharCode(c))
+        .join("");
+};
+
+const base64urlencode = (str: string) => btoa(str).replace(/\+/g, "-")
+    .replace(/\//g, "_")
+    .replace(/[=]+$/, "");
+
+const generatePKCEChallenge = async (verifier: string) => {
+    const hashed = await sha256(verifier);
+
+    return base64urlencode(hashed);
+};