diff --git a/.github/workflows/workflow.yml b/.github/workflows/workflow.yml
index 92eacc98d5..f14cf8be5b 100644
--- a/.github/workflows/workflow.yml
+++ b/.github/workflows/workflow.yml
@@ -28,11 +28,13 @@ jobs:
           - ocaml-variants.4.11.2+afl
           - ocaml-variants.4.12.1+options,ocaml-option-afl
           - ocaml-variants.4.13.1+options,ocaml-option-afl
-          - ocaml-variants.4.14.0+options,ocaml-option-afl
         local-packages:
           - |
             *.opam
             !cohttp-eio.opam
+            !cohttp-curl-async.opam
+            !cohttp-async.opam
+            !cohttp-bench.opam
 
     runs-on: ${{ matrix.os }}
 
@@ -40,6 +42,48 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v3
 
+      - name: Use OCaml ${{ matrix.ocaml-compiler }}
+        uses: ocaml/setup-ocaml@v2
+        with:
+          ocaml-compiler: ${{ matrix.ocaml-compiler }}
+          dune-cache: ${{ matrix.os == 'ubuntu-latest' }}
+          opam-depext: true
+          opam-depext-flags: --with-test
+          opam-local-packages: ${{ matrix.local-packages }}
+
+      - run: |
+          sudo apt update
+          sudo apt upgrade
+          opam depext conf-libcurl
+        if: ${{ matrix.os == 'ubuntu-latest' }}
+
+      - run: echo "PKG_CONFIG_PATH=$(brew --prefix openssl)/lib/pkgconfig" >>"$GITHUB_ENV"
+        if: ${{ matrix.os == 'macos-latest' }}
+
+      - run: opam install --with-test --deps-only http cohttp cohttp-lwt cohttp-lwt-unix cohttp-server-lwt-unix cohttp-mirage cohttp-curl-lwt cohttp-curl cohttp-top
+      - run: opam exec -- dune build http cohttp cohttp-lwt cohttp-lwt-unix cohttp-server-lwt-unix cohttp-mirage cohttp-curl-lwt cohttp-curl cohttp-top
+      - run: opam exec -- dune runtest http cohttp cohttp-lwt cohttp-lwt-unix cohttp-server-lwt-unix cohttp-mirage cohttp-curl-lwt cohttp-curl cohttp-top
+
+  build-test-cohttp-async:
+    if: github.event.pull_request.draft == false
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+          - ubuntu-latest
+          - macos-latest
+        ocaml-compiler:
+          - ocaml-variants.4.14.1+options,ocaml-option-afl
+        local-packages:
+          - |
+            *.opam
+            !cohttp-eio.opam
+
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
 
       - name: Use OCaml ${{ matrix.ocaml-compiler }}
         uses: ocaml/setup-ocaml@v2
@@ -59,9 +103,9 @@ jobs:
       - run: echo "PKG_CONFIG_PATH=$(brew --prefix openssl)/lib/pkgconfig" >>"$GITHUB_ENV"
         if: ${{ matrix.os == 'macos-latest' }}
 
-      - run: opam install --with-test --deps-only http cohttp cohttp-lwt cohttp-lwt-unix cohttp-server-lwt-unix cohttp-mirage cohttp-async cohttp-curl-async cohttp-curl-lwt cohttp-curl cohttp-top cohttp-bench
-      - run: opam exec -- dune build http cohttp cohttp-lwt cohttp-lwt-unix cohttp-server-lwt-unix cohttp-mirage cohttp-async cohttp-curl-async cohttp-curl-lwt cohttp-curl cohttp-top cohttp-bench
-      - run: opam exec -- dune runtest http cohttp cohttp-lwt cohttp-lwt-unix cohttp-server-lwt-unix cohttp-mirage cohttp-async cohttp-curl-async cohttp-curl-lwt cohttp-curl cohttp-top cohttp-bench
+      - run: opam install --with-test --deps-only http cohttp cohttp-lwt cohttp-lwt-unix cohttp-server-lwt-unix cohttp-async cohttp-curl-async cohttp-mirage cohttp-curl-lwt cohttp-curl cohttp-top cohttp-bench
+      - run: opam exec -- dune build http cohttp cohttp-lwt cohttp-lwt-unix cohttp-server-lwt-unix cohttp-async cohttp-curl-async cohttp-mirage cohttp-curl-lwt cohttp-curl cohttp-top cohttp-bench
+      - run: opam exec -- dune runtest http cohttp cohttp-lwt cohttp-lwt-unix cohttp-server-lwt-unix cohttp-async cohttp-curl-async cohttp-mirage cohttp-curl-lwt cohttp-curl cohttp-top cohttp-bench
 
   build-test-cohttp-eio:
     if: github.event.pull_request.draft == false
@@ -95,7 +139,5 @@ jobs:
             alpha: https://github.com/kit-ty-kate/opam-alpha-repository.git
 
       - run: opam install --with-test --deps-only cohttp-eio
-
       - run: opam exec -- dune build cohttp-eio
-
       - run: opam exec -- dune runtest cohttp-eio
diff --git a/CHANGES.md b/CHANGES.md
index 42d845566f..53c94d4e7a 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,10 +1,7 @@
 ## Unreleased
-
-- cohttp-lwt server: call conn_closed before drainig the body of response on error (pirbo)
-- cohttp-eio: Relax socket interface requirement on `Server.connection_handler`.
-
-## v6.0.0~alpha1 (2023-04-28)
-
+- cohttp-async, cohttp-curl-async: compatibility with core/async v0.16.0 (mseri, dkalinichenko-js #976)
+- cohttp-lwt server: call conn_closed before drainig the body of response on error (pirbo #982)
+- cohttp-eio: Relax socket interface requirement on `Server.connection_handler`. (mefyl #983)
 - cohttp,cohttp-async server: correctly close broken streams (reported by Stéphane Glondu, fix by samhot and anuragsoni)
 - cohttp-eio: remove unused code from tests to work with Eio 0.8 (talex5 #967)
 - Upgrade dune to v3.0 (bikallem #947)
diff --git a/cohttp-async.opam b/cohttp-async.opam
index 349faf3a79..228d3959ba 100644
--- a/cohttp-async.opam
+++ b/cohttp-async.opam
@@ -25,13 +25,13 @@ doc: "https://mirage.github.io/ocaml-cohttp/"
 bug-reports: "https://github.com/mirage/ocaml-cohttp/issues"
 depends: [
   "dune" {>= "3.0"}
-  "ocaml" {>= "4.08"}
+  "ocaml" {>= "4.14"}
   "http" {= version}
   "cohttp" {= version}
-  "async_kernel" {>= "v0.14.0"}
-  "async_unix" {>= "v0.14.0"}
-  "async" {>= "v0.14.0"}
-  "base" {>= "v0.11.0"}
+  "async_kernel" {>= "v0.16.0"}
+  "async_unix" {>= "v0.16.0"}
+  "async" {>= "v0.16.0"}
+  "base" {>= "v0.16"}
   "core" {with-test}
   "core_unix" {>= "v0.14.0"}
   "conduit-async" {>= "1.2.0"}
diff --git a/cohttp-async/bin/cohttp_server_async.ml b/cohttp-async/bin/cohttp_server_async.ml
index 6de184c4e0..8398e02725 100644
--- a/cohttp-async/bin/cohttp_server_async.ml
+++ b/cohttp-async/bin/cohttp_server_async.ml
@@ -50,7 +50,7 @@ let serve ~info ~docroot ~index uri path =
             | `No | `Unknown ->
                 (* Do a directory listing *)
                 Sys.ls_dir file_name
-                >>= Deferred.List.map ~f:(fun f ->
+                >>= Deferred.List.map ~how:`Parallel ~f:(fun f ->
                         let file_name = file_name / f in
                         try_with (fun () ->
                             Unix.stat file_name >>| fun stat ->
diff --git a/cohttp-async/examples/hello_world.ml b/cohttp-async/examples/hello_world.ml
index e3639ce91f..9005012aa0 100644
--- a/cohttp-async/examples/hello_world.ml
+++ b/cohttp-async/examples/hello_world.ml
@@ -18,8 +18,8 @@ let handler ~body:_ _sock req =
   | _ -> Server.respond_string ~status:`Not_found "Route not found"
 
 let start_server port () =
-  Caml.Printf.eprintf "Listening for HTTP on port %d\n" port;
-  Caml.Printf.eprintf "Try 'curl http://localhost:%d/test?hello=xyz'\n%!" port;
+  Stdlib.Printf.eprintf "Listening for HTTP on port %d\n" port;
+  Stdlib.Printf.eprintf "Try 'curl http://localhost:%d/test?hello=xyz'\n%!" port;
   Server.create ~on_handler_error:`Raise
     (Async.Tcp.Where_to_listen.of_port port)
     handler
diff --git a/cohttp-async/examples/receive_post.ml b/cohttp-async/examples/receive_post.ml
index 257318a612..88636b06fe 100644
--- a/cohttp-async/examples/receive_post.ml
+++ b/cohttp-async/examples/receive_post.ml
@@ -7,15 +7,15 @@ module Server = Cohttp_async.Server
 (* compile with: $ corebuild receive_post.native -pkg cohttp.async *)
 
 let start_server port () =
-  Caml.Printf.eprintf "Listening for HTTP on port %d\n" port;
-  Caml.Printf.eprintf "Try 'curl -X POST -d 'foo bar' http://localhost:%d\n"
+  Stdlib.Printf.eprintf "Listening for HTTP on port %d\n" port;
+  Stdlib.Printf.eprintf "Try 'curl -X POST -d 'foo bar' http://localhost:%d\n"
     port;
   Cohttp_async.Server.create ~on_handler_error:`Raise
     (Async.Tcp.Where_to_listen.of_port port) (fun ~body _ req ->
       match req |> Http.Request.meth with
       | `POST ->
           Body.to_string body >>= fun body ->
-          Caml.Printf.eprintf "Body: %s" body;
+          Stdlib.Printf.eprintf "Body: %s" body;
           Server.respond `OK
       | _ -> Server.respond `Method_not_allowed)
   >>= fun _ -> Deferred.never ()
diff --git a/cohttp-async/src/body.ml b/cohttp-async/src/body.ml
index dc31b523f9..5d430648ab 100644
--- a/cohttp-async/src/body.ml
+++ b/cohttp-async/src/body.ml
@@ -67,7 +67,7 @@ let write_body write_body (body : t) writer =
   match body with
   | `Empty -> return ()
   | `String s -> write_body writer s
-  | `Strings sl -> Deferred.List.iter sl ~f:(write_body writer)
+  | `Strings sl -> Deferred.List.iter ~how:`Sequential sl ~f:(write_body writer)
   | `Pipe p -> Pipe.iter p ~f:(write_body writer)
 
 let pipe_of_body read_chunk ic =
diff --git a/cohttp-async/src/client.ml b/cohttp-async/src/client.ml
index 0ad18074e9..c9535416da 100644
--- a/cohttp-async/src/client.ml
+++ b/cohttp-async/src/client.ml
@@ -120,7 +120,7 @@ let callv ?interrupt ?ssl_config uri reqs =
   Connection.connect ?interrupt ?ssl_config uri >>| fun connection ->
   let responses =
     Pipe.map' ~max_queue_length:1 reqs ~f:(fun reqs ->
-        Deferred.Queue.map reqs ~f:(fun (req, body) ->
+        Deferred.Queue.map ~how:`Sequential reqs ~f:(fun (req, body) ->
             Connection.request ~body connection req))
   in
   Pipe.closed responses
diff --git a/cohttp-async/src/io.ml b/cohttp-async/src/io.ml
index 36a151e106..60769ead1e 100644
--- a/cohttp-async/src/io.ml
+++ b/cohttp-async/src/io.ml
@@ -20,7 +20,7 @@ open Async_kernel
 module IO = struct
   module Writer = Async_unix.Writer
   module Reader = Async_unix.Reader
-  module Format = Caml.Format
+  module Format = Stdlib.Format
 
   let log_src_name = "cohttp.async.io"
   let src = Logs.Src.create log_src_name ~doc:"Cohttp Async IO module"
@@ -44,7 +44,7 @@ module IO = struct
         k ()
       in
       msgf @@ fun ?header:_ ?tags:_ fmt ->
-      Format.kfprintf k fmtr Caml.("@[" ^^ fmt ^^ "@]@.")
+      Format.kfprintf k fmtr Stdlib.("@[" ^^ fmt ^^ "@]@.")
     in
     { Logs.report }
 
@@ -58,11 +58,11 @@ module IO = struct
        Logs.set_reporter (default_reporter ()))
 
   let check_debug norm_fn debug_fn =
-    match Caml.Sys.getenv "COHTTP_DEBUG" with
+    match Stdlib.Sys.getenv "COHTTP_DEBUG" with
     | _ ->
         Lazy.force set_log;
         debug_fn
-    | exception Caml.Not_found -> norm_fn
+    | exception Stdlib.Not_found -> norm_fn
 
   type 'a t = 'a Deferred.t
 
diff --git a/cohttp-async/test/test_async_integration.ml b/cohttp-async/test/test_async_integration.ml
index 78f38b0249..d709759f0e 100644
--- a/cohttp-async/test/test_async_integration.ml
+++ b/cohttp-async/test/test_async_integration.ml
@@ -81,7 +81,7 @@ let ts =
         reqs |> Pipe.of_list |> Client.callv uri >>= fun responses ->
         responses |> Pipe.to_list >>= fun resps ->
         resps
-        |> Deferred.List.iter ~f:(fun (_resp, body) ->
+        |> Deferred.List.iter ~how:`Sequential ~f:(fun (_resp, body) ->
                let expected_body = body_q |> Queue.dequeue_exn in
                body |> Body.to_string >>| fun body ->
                assert_equal ~printer expected_body body)
@@ -113,7 +113,7 @@ let ts =
             ("Pipe with empty strings", Pipe.of_list [ ""; ""; "" ], true);
           ]
         in
-        Deferred.List.iter tests ~f:(fun (msg, pipe, expected) ->
+        Deferred.List.iter ~how:`Sequential tests ~f:(fun (msg, pipe, expected) ->
             is_empty (`Pipe pipe) >>| fun real ->
             assert_equal ~msg expected real)
         >>= fun () ->
diff --git a/cohttp-bench/async_server.ml b/cohttp-bench/async_server.ml
index d662bdb86b..632e731271 100644
--- a/cohttp-bench/async_server.ml
+++ b/cohttp-bench/async_server.ml
@@ -13,7 +13,7 @@ let start_server port () =
     handler
   >>= fun server ->
   Deferred.forever () (fun () ->
-      after Time.Span.(of_sec 0.5) >>| fun () ->
+      after Time_float.Span.(of_sec 0.5) >>| fun () ->
       Log.Global.printf "Active connections: %d" (Server.num_connections server));
   Deferred.never ()
 
diff --git a/cohttp-curl-async.opam b/cohttp-curl-async.opam
index 1a8dbd2203..93b977010b 100644
--- a/cohttp-curl-async.opam
+++ b/cohttp-curl-async.opam
@@ -25,7 +25,7 @@ depends: [
   "http" {= version}
   "stringext"
   "cohttp-curl" {= version}
-  "core"
+  "core" {>= "v0.16.0"}
   "core_unix" {>= "v0.14.0"}
   "async_kernel"
   "async_unix"
diff --git a/cohttp-curl-async/bin/curl.ml b/cohttp-curl-async/bin/curl.ml
index b1d532fd70..517b6d7ca3 100644
--- a/cohttp-curl-async/bin/curl.ml
+++ b/cohttp-curl-async/bin/curl.ml
@@ -3,7 +3,7 @@ module Curl = Cohttp_curl_async
 module Sexp = Sexplib0.Sexp
 open Async_kernel
 module Writer = Async_unix.Writer
-module Time = Core.Time
+module Time = Core.Time_float
 
 let ( let* ) x f = Deferred.bind x ~f
 
diff --git a/cohttp-curl-async/src/cohttp_curl_async.ml b/cohttp-curl-async/src/cohttp_curl_async.ml
index 7a47d611c4..e955047cd4 100644
--- a/cohttp-curl-async/src/cohttp_curl_async.ml
+++ b/cohttp-curl-async/src/cohttp_curl_async.ml
@@ -1,5 +1,5 @@
 open Async_kernel
-module Time = Core.Time
+module Time = Core.Time_float
 module Fd = Async_unix.Fd
 module Clock = Async_unix.Clock
 
@@ -164,7 +164,7 @@ module Request = struct
     let base =
       let timeout_ms =
         Option.map
-          (fun timeout -> Core.Time.Span.to_ms timeout |> int_of_float)
+          (fun timeout -> Time.Span.to_ms timeout |> int_of_float)
           timeout
       in
       Cohttp_curl.Request.create ?timeout_ms ?headers method_ ~uri ~input
diff --git a/cohttp-curl-async/src/cohttp_curl_async.mli b/cohttp-curl-async/src/cohttp_curl_async.mli
index ab9fc496f1..274e9d6cc7 100644
--- a/cohttp-curl-async/src/cohttp_curl_async.mli
+++ b/cohttp-curl-async/src/cohttp_curl_async.mli
@@ -51,7 +51,7 @@ module Request : sig
       handled. *)
 
   val create :
-    ?timeout:Core.Time.Span.t (** timeout for the request *) ->
+    ?timeout:Core.Time_float.Span.t (** timeout for the request *) ->
     ?headers:Http.Header.t (** http headers *) ->
     Http.Method.t (** http method *) ->
     uri:string (** uri *) ->
diff --git a/dune-project b/dune-project
index 948b48a3b1..b57c16067c 100644
--- a/dune-project
+++ b/dune-project
@@ -174,13 +174,13 @@ should also be fine under Windows too.
   (cohttp
    (= :version))
   (async_kernel
-   (>= v0.14.0))
+   (>= v0.16.0))
   (async_unix
-   (>= v0.14.0))
+   (>= v0.16.0))
   (async
-   (>= v0.14.0))
+   (>= v0.16.0))
   (base
-   (>= v0.11.0))
+   (>= v0.16.0))
   (core :with-test)
   (core_unix
    (>= v0.14.0))
@@ -317,7 +317,7 @@ should also be fine under Windows too.
   stringext
   (cohttp-curl
    (= :version))
-  core
+  (core (>= v0.16.0))
   (core_unix (>= v0.14.0))
   async_kernel
   async_unix