diff --git a/dune-project b/dune-project
index 6446bd94..cd0328d3 100644
--- a/dune-project
+++ b/dune-project
@@ -39,3 +39,12 @@
     (iostream-camlzip (>= 0.2.1))
     (logs :with-test)
     (odoc :with-doc)))
+
+(package
+  (name tiny_httpd_eio)
+  (synopsis "Use eio for tiny_httpd")
+  (depends
+    (tiny_httpd (= :version))
+    eio
+    (logs :with-test)
+    (odoc :with-doc)))
diff --git a/src/eio/dune b/src/eio/dune
new file mode 100644
index 00000000..37431aba
--- /dev/null
+++ b/src/eio/dune
@@ -0,0 +1,8 @@
+
+(library
+  (name tiny_httpd_eio)
+  (public_name tiny_httpd_eio)
+  (synopsis "An EIO-based backend for Tiny_httpd")
+  (flags :standard -safe-string -warn-error -a+8)
+  (libraries tiny_httpd eio eio.unix))
+
diff --git a/src/eio/tiny_httpd_eio.ml b/src/eio/tiny_httpd_eio.ml
new file mode 100644
index 00000000..e58d1b6b
--- /dev/null
+++ b/src/eio/tiny_httpd_eio.ml
@@ -0,0 +1,207 @@
+module IO = Tiny_httpd.IO
+module H = Tiny_httpd.Server
+module Pool = Tiny_httpd.Pool
+module Slice = IO.Slice
+module Log = Tiny_httpd.Log
+
+let ( let@ ) = ( @@ )
+
+type 'a with_args =
+  ?addr:string ->
+  ?port:int ->
+  ?unix_sock:string ->
+  ?max_connections:int ->
+  ?max_buf_pool_size:int ->
+  stdenv:Eio_unix.Stdenv.base ->
+  sw:Eio.Switch.t ->
+  'a
+
+let get_max_connection_ ?(max_connections = 64) () : int =
+  let max_connections = max 4 max_connections in
+  max_connections
+
+let buf_size = 16 * 1024
+
+let eio_ipaddr_to_unix (a : _ Eio.Net.Ipaddr.t) : Unix.inet_addr =
+  (* TODO: for ipv4 we really could do it faster via sprintf 🙄 *)
+  Unix.inet_addr_of_string (Format.asprintf "%a" Eio.Net.Ipaddr.pp a)
+
+let eio_sock_addr_to_unix (a : Eio.Net.Sockaddr.stream) : Unix.sockaddr =
+  match a with
+  | `Tcp (h, p) -> Unix.ADDR_INET (eio_ipaddr_to_unix h, p)
+  | `Unix s -> Unix.ADDR_UNIX s
+
+let ic_of_flow ~buf_pool:ic_pool (flow : _ Eio.Net.stream_socket) : IO.Input.t =
+  let cstruct = Pool.Raw.acquire ic_pool in
+
+  object
+    inherit Iostream.In_buf.t_from_refill ()
+
+    method private refill (sl : Slice.t) =
+      assert (sl.len = 0);
+      let cap = min (Bytes.length sl.bytes) (Cstruct.length cstruct) in
+
+      match Eio.Flow.single_read flow (Cstruct.sub cstruct 0 cap) with
+      | exception End_of_file ->
+        Log.debug (fun k -> k "read: eof");
+        ()
+      | n ->
+        Log.debug (fun k -> k "read %d bytes..." n);
+        Cstruct.blit_to_bytes cstruct 0 sl.bytes 0 n;
+        sl.off <- 0;
+        sl.len <- n
+
+    method close () =
+      Pool.Raw.release ic_pool cstruct;
+      Eio.Flow.shutdown flow `Receive
+  end
+
+let oc_of_flow ~buf_pool:oc_pool (flow : _ Eio.Net.stream_socket) : IO.Output.t
+    =
+  (* write buffer *)
+  let wbuf : Cstruct.t = Pool.Raw.acquire oc_pool in
+  let offset = ref 0 in
+
+  object (self)
+    method flush () : unit =
+      if !offset > 0 then (
+        Eio.Flow.write flow [ Cstruct.sub wbuf 0 !offset ];
+        offset := 0
+      )
+
+    method output buf i len =
+      let i = ref i in
+      let len = ref len in
+
+      while !len > 0 do
+        let available = Cstruct.length wbuf - !offset in
+        let n = min !len available in
+        Cstruct.blit_from_bytes buf !i wbuf !offset n;
+        offset := !offset + n;
+        i := !i + n;
+        len := !len - n;
+
+        if !offset = Cstruct.length wbuf then self#flush ()
+      done
+
+    method output_char c =
+      if !offset = Cstruct.length wbuf then self#flush ();
+      Cstruct.set_char wbuf !offset c;
+      incr offset;
+      if !offset = Cstruct.length wbuf then self#flush ()
+
+    method close () =
+      Pool.Raw.release oc_pool wbuf;
+      Eio.Flow.shutdown flow `Send
+  end
+
+let io_backend ?addr ?port ?unix_sock ?max_connections ?max_buf_pool_size
+    ~(stdenv : Eio_unix.Stdenv.base) ~(sw : Eio.Switch.t) () :
+    (module H.IO_BACKEND) =
+  let addr, port, (sockaddr : Eio.Net.Sockaddr.stream) =
+    match addr, port, unix_sock with
+    | _, _, Some s -> Printf.sprintf "unix:%s" s, 0, `Unix s
+    | addr, port, None ->
+      let addr = Option.value ~default:"127.0.0.1" addr in
+      let sockaddr, port =
+        match Eio.Net.getaddrinfo stdenv#net addr, port with
+        | `Tcp (h, _) :: _, None ->
+          let p = 8080 in
+          `Tcp (h, p), p
+        | `Tcp (h, _) :: _, Some p -> `Tcp (h, p), p
+        | _ ->
+          failwith @@ Printf.sprintf "Could not parse TCP address from %S" addr
+      in
+      addr, port, sockaddr
+  in
+
+  let module M = struct
+    let init_addr () = addr
+    let init_port () = port
+    let get_time_s () = Unix.gettimeofday ()
+    let max_connections = get_max_connection_ ?max_connections ()
+
+    let pool_size =
+      match max_buf_pool_size with
+      | Some n -> n
+      | None -> min 4096 (max_connections * 2)
+
+    let cstruct_pool =
+      Pool.create ~max_size:max_connections
+        ~mk_item:(fun () -> Cstruct.create buf_size)
+        ()
+
+    let tcp_server () : IO.TCP_server.builder =
+      {
+        IO.TCP_server.serve =
+          (fun ~after_init ~handle () : unit ->
+            let running = Atomic.make true in
+            let active_conns = Atomic.make 0 in
+
+            Eio.Switch.on_release sw (fun () -> Atomic.set running false);
+            let net = Eio.Stdenv.net stdenv in
+
+            (* main server socket *)
+            let sock =
+              let backlog = max_connections in
+              Eio.Net.listen ~reuse_addr:true ~reuse_port:true ~backlog ~sw net
+                sockaddr
+            in
+
+            let tcp_server : IO.TCP_server.t =
+              {
+                running = (fun () -> Atomic.get running);
+                stop =
+                  (fun () ->
+                    Atomic.set running false;
+                    Eio.Switch.fail sw Exit);
+                endpoint =
+                  (fun () ->
+                    (* TODO: find the real port *)
+                    addr, port);
+                active_connections = (fun () -> Atomic.get active_conns);
+              }
+            in
+
+            after_init tcp_server;
+
+            while Atomic.get running do
+              Eio.Net.accept_fork ~sw
+                ~on_error:(fun exn ->
+                  Log.error (fun k ->
+                      k "error in client handler: %s" (Printexc.to_string exn)))
+                sock
+                (fun flow client_addr ->
+                  Atomic.incr active_conns;
+                  let@ () =
+                    Fun.protect ~finally:(fun () ->
+                        Log.debug (fun k ->
+                            k "Tiny_httpd_eio: client handler returned");
+                        Atomic.decr active_conns)
+                  in
+                  let ic = ic_of_flow ~buf_pool:cstruct_pool flow in
+                  let oc = oc_of_flow ~buf_pool:cstruct_pool flow in
+
+                  Log.debug (fun k ->
+                      k "handling client on %a…" Eio.Net.Sockaddr.pp client_addr);
+                  let client_addr_unix = eio_sock_addr_to_unix client_addr in
+                  try handle.handle ~client_addr:client_addr_unix ic oc
+                  with exn ->
+                    let bt = Printexc.get_raw_backtrace () in
+                    Log.error (fun k ->
+                        k "Client handler for %a failed with %s\n%s"
+                          Eio.Net.Sockaddr.pp client_addr
+                          (Printexc.to_string exn)
+                          (Printexc.raw_backtrace_to_string bt)))
+            done);
+      }
+  end in
+  (module M)
+
+let create ?addr ?port ?unix_sock ?max_connections ?max_buf_pool_size ~stdenv
+    ~sw ?buf_size ?middlewares () : H.t =
+  let backend =
+    io_backend ?addr ?port ?unix_sock ?max_buf_pool_size ?max_connections
+      ~stdenv ~sw ()
+  in
+  H.create_from ?buf_size ?middlewares ~backend ()
diff --git a/src/eio/tiny_httpd_eio.mli b/src/eio/tiny_httpd_eio.mli
new file mode 100644
index 00000000..3183ef49
--- /dev/null
+++ b/src/eio/tiny_httpd_eio.mli
@@ -0,0 +1,31 @@
+(** Tiny httpd EIO backend.
+
+    This replaces the threads + Unix blocking syscalls of {!Tiny_httpd_server}
+    with an Eio-based cooperative system.
+
+    {b NOTE}: this is very experimental and will absolutely change over time,
+    especially since Eio itself is also subject to change.
+    @since NEXT_RELEASE *)
+
+(* TODO: pass in a switch *)
+
+type 'a with_args =
+  ?addr:string ->
+  ?port:int ->
+  ?unix_sock:string ->
+  ?max_connections:int ->
+  ?max_buf_pool_size:int ->
+  stdenv:Eio_unix.Stdenv.base ->
+  sw:Eio.Switch.t ->
+  'a
+
+val io_backend : (unit -> (module Tiny_httpd.Server.IO_BACKEND)) with_args
+(** Create a server *)
+
+val create :
+  (?buf_size:int ->
+  ?middlewares:([ `Encoding | `Stage of int ] * Tiny_httpd.Middleware.t) list ->
+  unit ->
+  Tiny_httpd.Server.t)
+  with_args
+(** Create a server *)
diff --git a/tiny_httpd_eio.opam b/tiny_httpd_eio.opam
new file mode 100644
index 00000000..cdc15a35
--- /dev/null
+++ b/tiny_httpd_eio.opam
@@ -0,0 +1,31 @@
+# This file is generated by dune, edit dune-project instead
+opam-version: "2.0"
+version: "0.19"
+synopsis: "Use eio for tiny_httpd"
+maintainer: ["c-cube"]
+authors: ["c-cube"]
+license: "MIT"
+homepage: "https://github.com/c-cube/tiny_httpd/"
+bug-reports: "https://github.com/c-cube/tiny_httpd/issues"
+depends: [
+  "dune" {>= "3.2"}
+  "tiny_httpd" {= version}
+  "eio"
+  "logs" {with-test}
+  "odoc" {with-doc}
+]
+build: [
+  ["dune" "subst"] {dev}
+  [
+    "dune"
+    "build"
+    "-p"
+    name
+    "-j"
+    jobs
+    "@install"
+    "@runtest" {with-test}
+    "@doc" {with-doc}
+  ]
+]
+dev-repo: "git+https://github.com/c-cube/tiny_httpd.git"