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docs: websockets do not work with vite dev server pre-Deno 2.8 and Fresh 2.4 #3822

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bartlomieju merged 2 commits into from
May 27, 2026
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docs: websockets do not work with vite dev server pre-Deno 2.8 and Fresh 2.4 #3822

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a1d530d
update docs to reflect the fact that websockets do not work with vite…
will-weiss May 26, 2026
70f8e62
docs: reflect that WS works in Vite dev on Fresh 2.4+ / Deno 2.8+
bartlomieju May 27, 2026
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18 changes: 18 additions & 0 deletions docs/latest/advanced/websockets.md
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Expand Up @@ -6,6 +6,24 @@ description: |
Fresh provides built-in helpers for upgrading HTTP connections to WebSockets.
There are two main approaches depending on your use case.

> [info]: WebSocket upgrades under the Vite dev server (`deno task dev`) require
> **Fresh 2.4+** and **Deno 2.8+**. On older versions `Deno.upgradeWebSocket()`
> cannot complete the 101 handshake for requests Vite forwards from its Node
> HTTP server, so `ctx.upgrade()` and `app.ws()` silently hang and the `open`
> handler is never invoked.
>
> If you're stuck on an older Deno or Fresh, exercise WebSocket endpoints with a
> production-style build instead:
>
> ```sh
> deno task build && deno task start
> ```
>
> This runs `deno serve` directly, so `Deno.upgradeWebSocket()` works as
> expected. Alternatively, run a separate Deno entry point (e.g.
> `deno serve -A main.ts`) alongside Vite, or host the WebSocket server as a
> sidecar on its own port.

## Quick start with `app.ws()`

The simplest way to add a WebSocket endpoint:
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