# WebTransport server-readiness checklist

> Interactive checklist for a WebTransport server: UDP, HTTP/3, certificates, settings, CONNECT, origin, firewall. Copy a what-to-check-next report.

URL: https://webtransport.day/tools/server-checklist/
Updated: 2026-10-28
Facts checked: 2026-10-28

**Short answer:** A WebTransport server needs seven things in place: a reachable UDP port, HTTP/3 over QUIC, a certificate the browser accepts, the WebTransport settings enabled, extended CONNECT handling at the right path, an origin policy that allows your page, and a firewall that passes UDP. Tick what is done and copy a report of what to check next.

This tool runs in the browser and needs JavaScript; the sections below describe what it does.

## How do I use the checklist?

Work through the items from top to bottom, tick each one you have confirmed on the server you are testing, and copy the report of unchecked items. The order follows the path a connection takes: network first, then QUIC and TLS, then HTTP/3 and WebTransport, then policy. If you tick everything and the connection still fails, test with the [WebTransport tester](/tools/webtransport-tester/) and read [debugging handshake errors](/guides/debug-webtransport-handshake-errors/).

## What does each item mean?

Each item states what to verify and why, with the source it comes from. Names such as the HTTP/3 settings are defined by the IETF draft, which can change.

## FAQ

### Does this checklist test my server?

No. It cannot open QUIC connections to your server for you; it is a checklist you complete by hand, and it produces a copyable list of what to check next. To test a connection from your browser, use the WebTransport tester.

### Why are some setting names marked draft-specific?

WebTransport over HTTP/3 is still an IETF draft, and the names of some HTTP/3 settings are defined by that draft. They may change before it becomes an RFC, so check the draft your server library implements.

### Does my page need to be on the same origin as the server?

No. Browsers send an Origin header, and the server decides which origins to accept. A server that rejects your page origin is a common cause of failed connections.

## Sources

- [W3C: WebTransport](https://www.w3.org/TR/webtransport/)
- [IETF draft-ietf-webtrans-http3: WebTransport over HTTP/3](https://datatracker.ietf.org/doc/draft-ietf-webtrans-http3/)
- [RFC 9114: HTTP/3](https://www.rfc-editor.org/rfc/rfc9114)
- [RFC 9000: QUIC](https://www.rfc-editor.org/rfc/rfc9000)
- [RFC 9221: An Unreliable Datagram Extension to QUIC](https://www.rfc-editor.org/rfc/rfc9221)
- [MDN: WebTransport() constructor (serverCertificateHashes)](https://developer.mozilla.org/en-US/docs/Web/API/WebTransport/WebTransport)