diff --git a/CHANGELOG.md b/CHANGELOG.md
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--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,5 @@
+# Revision history for jsaddle-wasm
+
+## 0.0.0.0 -- 2024-10-20
+
+ * First version.
diff --git a/LICENSE b/LICENSE
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--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,121 @@
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diff --git a/README.md b/README.md
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--- /dev/null
+++ b/README.md
@@ -0,0 +1,91 @@
+# jsaddle-wasm
+[![CI](https://github.com/amesgen/jsaddle-wasm/workflows/ci-wasm/badge.svg)](https://github.com/amesgen/jsaddle-wasm/actions)
+[![Hackage](https://img.shields.io/hackage/v/jsaddle-wasm)](https://hackage.haskell.org/package/jsaddle-wasm
+[![Haddocks](https://img.shields.io/badge/documentation-Haddocks-purple)](https://hackage.haskell.org/package/jsaddle-wasm/docs/Language-Javascript-JSaddle-Wasm.html))
+
+Run [JSaddle][] `JSM` actions with the [GHC WASM backend][].
+
+This can for example be used to compile and run [Miso][] or [Reflex][] apps in the browser.
+
+> [!IMPORTANT]
+> This project is in an early stage.
+
+## Examples
+
+### Miso
+
+Several Miso examples: https://github.com/tweag/ghc-wasm-miso-examples
+
+## How to use
+
+Install a WASM-enabled GHC with support for the WASM JSFFI from [ghc-wasm-meta][] (GHC 9.10 or newer).
+
+Assuming you built your application as an `app :: JSM ()`:
+
+```haskell
+import Language.Javascript.JSaddle.Wasm qualified as JSaddle.Wasm
+
+foreign export javascript "hs_start" main :: IO ()
+
+main :: IO ()
+main = JSaddle.Wasm.run app
+```
+
+Build the WASM binary with the following GHC options:
+```cabal
+ghc-options: -no-hs-main -optl-mexec-model=reactor "-optl-Wl,--export=hs_start"
+```
+
+Now, run the post-linker script as described in the [GHC User's Guide][ghc-users-guide-js-api]; we will call the resulting JavaScript file `ghc_wasm_jsffi.js`.
+
+Then, following the [GHC User's Guide][ghc-users-guide-js-api], you can run the WASM binary in the browser via e.g. [browser_wasi_shim][]:
+```javascript
+import { WASI, OpenFile, File, ConsoleStdout } from "@bjorn3/browser_wasi_shim";
+import ghc_wasm_jsffi from "./ghc_wasm_jsffi.js";
+
+const fds = [
+  new OpenFile(new File([])), // stdin
+  ConsoleStdout.lineBuffered((msg) => console.log(`[WASI stdout] ${msg}`)),
+  ConsoleStdout.lineBuffered((msg) => console.warn(`[WASI stderr] ${msg}`)),
+];
+const options = { debug: false };
+const wasi = new WASI([], [], fds, options);
+
+const instance_exports = {};
+const { instance } = await WebAssembly.instantiateStreaming(fetch("app.wasm"), {
+  wasi_snapshot_preview1: wasi.wasiImport,
+  ghc_wasm_jsffi: ghc_wasm_jsffi(instance_exports),
+});
+Object.assign(instance_exports, instance.exports);
+
+wasi.initialize(instance);
+await instance.exports.hs_start();
+```
+
+## Potential future work
+
+ - Take a closer look at synchronous callbacks (no special handling currently, but basic things like `stopPropagation` already seem to work fine).
+ - Testing (e.g. via Selenium).
+ - Add logging/stats.
+ - Performance/benchmarking (not clear that this is actually a bottleneck for most applications).
+    - Optimize existing command-based implementation.
+       - Reuse buffers
+       - Use a serialization format more efficient than JSON.
+    - Implement `ghcjs-dom` API directly via the WASM JS FFI.
+
+      This would involve creating a `ghcjs-dom-wasm` package by adapting the FFI import syntax from `ghcjs-dom-jsffi`/`ghcjs-dom-javascript` appropriately.
+
+      Currently, the generic `ghcjs-dom-jsaddle` seems to work fine, so it seems sensible to wait with this until benchmarks or other concerns motivate this.
+
+## Related projects
+
+ - [WebGHC/jsaddle-wasm](https://github.com/WebGHC/jsaddle-wasm) for the analogue for [WebGHC][] instead of the [GHC WASM backend][].
+
+[JSaddle]: https://github.com/ghcjs/jsaddle
+[GHC WASM backend]: https://www.tweag.io/blog/2022-11-22-wasm-backend-merged-in-ghc
+[Miso]: https://github.com/dmjio/miso
+[Reflex]: https://github.com/reflex-frp/reflex
+[ghc-wasm-meta]: https://gitlab.haskell.org/ghc/ghc-wasm-meta
+[browser_wasi_shim]: https://github.com/bjorn3/browser_wasi_shim
+[ghc-users-guide-js-api]: https://ghc.gitlab.haskell.org/ghc/doc/users_guide/wasm.html#the-javascript-api
+[WebGHC]: https://webghc.github.io
diff --git a/jsaddle-wasm.cabal b/jsaddle-wasm.cabal
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--- /dev/null
+++ b/jsaddle-wasm.cabal
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+cabal-version: 3.0
+name: jsaddle-wasm
+version: 0.0.0.0
+synopsis: Run JSaddle @JSM@ with the GHC WASM backend
+description: Run JSaddle @JSM@ with the GHC WASM backend.
+category: Web, Javascript
+homepage: https://github.com/amesgen/jsaddle-wasm
+bug-reports: https://github.com/amesgen/jsaddle-wasm/issues
+license: CC0-1.0
+license-file: LICENSE
+extra-source-files: README.md
+author: amesgen
+maintainer: amesgen@amesgen.de
+extra-doc-files: CHANGELOG.md
+
+source-repository head
+  location: https://github.com/amesgen/jsaddle-wasm
+  type: git
+
+common common
+  ghc-options:
+    -Wall
+    -Wunused-packages
+    -Wredundant-constraints
+
+  default-language: GHC2021
+  default-extensions:
+    BlockArguments
+    OverloadedStrings
+
+library
+  import: common
+  hs-source-dirs: src
+  exposed-modules:
+    Language.Javascript.JSaddle.Wasm
+
+  other-modules:
+    Language.Javascript.JSaddle.Wasm.Internal
+
+  build-depends:
+    base >=4.16 && <5,
+    jsaddle ^>=0.9,
+
+  if arch(wasm32)
+    build-depends:
+      aeson >=2 && <2.3,
+      async ^>=2.2,
+      bytestring >=0.11 && <0.13,
+      ghc-experimental ^>=0.1,
+      stm ^>=2.5,
+
+    hs-source-dirs: src-wasm
+  else
+    hs-source-dirs: src-native
diff --git a/src-native/Language/Javascript/JSaddle/Wasm/Internal.hs b/src-native/Language/Javascript/JSaddle/Wasm/Internal.hs
new file mode 100644
--- /dev/null
+++ b/src-native/Language/Javascript/JSaddle/Wasm/Internal.hs
@@ -0,0 +1,6 @@
+module Language.Javascript.JSaddle.Wasm.Internal (run) where
+
+import Language.Javascript.JSaddle.Types (JSM)
+
+run :: JSM () -> IO ()
+run _ = fail "Language.Javascript.JSaddle.Wasm.run: only works on WASM backend"
diff --git a/src-wasm/Language/Javascript/JSaddle/Wasm/Internal.hs b/src-wasm/Language/Javascript/JSaddle/Wasm/Internal.hs
new file mode 100644
--- /dev/null
+++ b/src-wasm/Language/Javascript/JSaddle/Wasm/Internal.hs
@@ -0,0 +1,89 @@
+module Language.Javascript.JSaddle.Wasm.Internal (run) where
+
+import Control.Concurrent.Async qualified as Async
+import Control.Concurrent.STM
+import Control.Exception (evaluate)
+import Data.Aeson qualified as A
+import Data.ByteString (ByteString)
+import Data.ByteString.Internal qualified as BI
+import Data.ByteString.Lazy.Char8 qualified as BLC8
+import Data.ByteString.Unsafe qualified as BU
+import Foreign.Ptr (Ptr)
+import GHC.Wasm.Prim (JSString, JSVal)
+import GHC.Wasm.Prim qualified
+import Language.Javascript.JSaddle.Run (runJavaScript)
+import Language.Javascript.JSaddle.Run.Files qualified as JSaddle.Files
+import Language.Javascript.JSaddle.Types (Batch, JSM)
+
+run :: JSM () -> IO ()
+run entryPoint = do
+  -- TODO rather use a bounded (even size 1) queue?
+  batchQueue :: TQueue Batch <- newTQueueIO
+
+  let sendBatch :: Batch -> IO ()
+      sendBatch = atomically . writeTQueue batchQueue
+
+  (processResult, _processSyncResult, start) <-
+    runJavaScript sendBatch entryPoint
+
+  processResultCallback <- mkPullCallback \s -> do
+    bs <- jsStringToByteString s
+    case A.eitherDecodeStrict bs of
+      Left e -> fail $ "jsaddle: received invalid JSON: " <> show e
+      Right r -> processResult r
+
+  readBatchCallback <- mkPushCallback do
+    batch <- atomically $ readTQueue batchQueue
+    byteStringToJSString $ BLC8.toStrict $ A.encode batch
+
+  let jsaddleRunner :: IO ()
+      jsaddleRunner = do
+        s <-
+          byteStringToJSString . BLC8.toStrict . BLC8.unlines $
+            [ JSaddle.Files.ghcjsHelpers,
+              JSaddle.Files.initState,
+              "(async () => {",
+              "  while (true) {",
+              "    const batch = JSON.parse(await readBatch());",
+              JSaddle.Files.runBatch
+                (\r -> "processResult(JSON.stringify(" <> r <> "));")
+                -- TODO handle synchronous stuff (see processSyncResult)
+                Nothing,
+              "  }",
+              "})();"
+            ]
+        evaluate =<< js_eval s processResultCallback readBatchCallback
+
+  Async.concurrently_ start jsaddleRunner
+
+-- Utilities:
+
+foreign import javascript "wrapper" mkPullCallback :: (JSString -> IO ()) -> IO JSVal
+
+foreign import javascript "wrapper" mkPushCallback :: IO JSString -> IO JSVal
+
+foreign import javascript safe "new Function('processResult','readBatch',`(()=>{${$1}})()`)($2, $3)"
+  js_eval :: JSString -> JSVal -> JSVal -> IO ()
+
+-- Conversion JSString <-> ByteString
+
+foreign import javascript unsafe "$1.length"
+  js_stringLength :: JSString -> IO Int
+
+foreign import javascript unsafe "(new TextEncoder()).encodeInto($1, new Uint8Array(__exports.memory.buffer, $2, $3)).written"
+  js_encodeInto :: JSString -> Ptr a -> Int -> IO Int
+
+jsStringToByteString :: JSString -> IO ByteString
+jsStringToByteString s = do
+  len <- js_stringLength s
+  -- see https://developer.mozilla.org/en-US/docs/Web/API/TextEncoder/encodeInto#buffer_sizing
+  -- (could also use another strategy described there)
+  let lenMax = len * 3
+  BI.createUptoN lenMax \buf -> js_encodeInto s buf lenMax
+
+foreign import javascript unsafe "(new TextDecoder('utf-8', {fatal: true})).decode(new Uint8Array(__exports.memory.buffer, $1, $2))"
+  js_toJSString :: Ptr a -> Int -> IO JSString
+
+byteStringToJSString :: ByteString -> IO JSString
+byteStringToJSString bs =
+  BU.unsafeUseAsCStringLen bs $ uncurry js_toJSString
diff --git a/src/Language/Javascript/JSaddle/Wasm.hs b/src/Language/Javascript/JSaddle/Wasm.hs
new file mode 100644
--- /dev/null
+++ b/src/Language/Javascript/JSaddle/Wasm.hs
@@ -0,0 +1,13 @@
+module Language.Javascript.JSaddle.Wasm (run) where
+
+import Language.Javascript.JSaddle.Types (JSM)
+import Language.Javascript.JSaddle.Wasm.Internal qualified as Internal
+
+-- | Run a 'JSM' action via the WASM JavaScript FFI.
+--
+-- See the [README](https://github.com/amesgen/jsaddle-wasm) for more details.
+--
+-- While this package also compiles on non-WASM GHCs for convenience, running
+-- this function will immediately fail.
+run :: JSM () -> IO ()
+run = Internal.run