# WebTransport and serverless or edge platforms: what is possible

> Can serverless or edge platforms act as a WebTransport server? What Cloudflare, AWS, Google Cloud, Vercel, Fastly and others document, checked 2026-10-28.

URL: https://webtransport.day/serverless/
Updated: 2026-10-31
Facts checked: 2026-10-28

**Notice:** This domain previously hosted a public WebTransport echo server. That service is no longer running here. This site is now an independent developer resource and is not affiliated with the original service.

**Short answer:** We found no official documentation from Cloudflare, AWS, Google Cloud, Vercel, Fastly, Azure, Deno or Akamai saying their serverless or edge function layer can act as a WebTransport server. Documented routes are a server you run on a host with open UDP, or managed Media over QUIC relays. Checked 2026-10-28.

## Key facts

- **Providers checked:** Cloudflare, AWS, Google Cloud, Azure, Vercel, Fastly, Deno, Fly.io, Akamai
- **Result:** No provider documents a function layer acting as a WebTransport server
- **Documented route:** A server you run on a host with an open UDP port

## Can a serverless or edge platform run a WebTransport server?

As of 2026-10-28, we found no provider documentation that says its serverless or edge function layer can act as a WebTransport server. That is a statement about documentation, not a proof that it cannot work. The routes that providers do document are running your own QUIC-capable server on a host with a reachable UDP port, and managed Media over QUIC (MoQ) relays on some networks.

## Why is WebTransport a poor fit for request/response functions?



A WebTransport session is a long-lived connection. A browser opens it with an HTTP/3 extended CONNECT request, and the session then carries many streams and datagrams over one QUIC connection. The IETF's WebTransport over HTTP/3 draft is still a draft (draft-16 as we checked), and it requires the server to send specific HTTP/3 settings before clients may start a session.

Serverless platforms are built around short invocations that return a response. Their documentation reflects that:

- AWS Lambda describes itself as short-lived compute with a 15-minute maximum.
- Vercel and Google Cloud Run document WebSockets, but close them when the function or request timeout is reached and tell you to reconnect and keep state elsewhere.
- Several CDNs terminate HTTP/3 only between the user and the edge. CloudFront and Azure Front Door document HTTP/1.1 to the origin, and Fastly and Cloudflare document that HTTP/3 to the origin is not supported. That is a fact about those products; connecting it to WebTransport is our inference, not a vendor statement.

> **Known unknowns:** "Not documented" is not "unsupported". We could not confirm whether Cloudflare's MoQ relays use WebTransport or raw QUIC, we found nothing in Netlify's documentation either way, and some provider pages blocked automated reading. Check each provider's current documentation before deciding.

## What do providers document today?

Verdicts describe what we could find in official documentation on 2026-10-28. "Not documented" is not "unsupported".

| Platform | What the docs say | WebTransport server |
|---|---|---|
| [Cloudflare Workers](https://developers.cloudflare.com/workers/runtime-apis/) | WebSockets (server and client), outbound TCP sockets, inbound HTTP/3 to the edge. Inbound TCP is listed as coming soon. | Not documented. No WebTransport or UDP in the runtime API list. |
| [Cloudflare proxy and Spectrum](https://developers.cloudflare.com/spectrum/reference/limitations/) | HTTP/3 from clients to Cloudflare. Docs state HTTP/3 to origin is not yet supported. Spectrum proxies TCP and UDP (Enterprise for custom apps). | Not documented for QUIC or WebTransport. |
| [Cloudflare MoQ relays](https://developers.cloudflare.com/moq/) | Managed relays in beta, created in the dashboard, token-gated. | Media relays, not a general WebTransport server. The docs we read do not say whether WebTransport or raw QUIC is used. |
| [Fastly Compute](https://www.fastly.com/documentation/guides/full-site-delivery/performance/enabling-http3-for-fastly-services/) | HTTP/3 on the user side; WebSocket passthrough. HTTP/3 to origin unsupported. | Not documented. |
| [Vercel Functions](https://vercel.com/docs/functions/websockets) | WebSockets, pinned to an instance and closed at the maximum duration. | Not documented. |
| [AWS CloudFront, API Gateway, Lambda](https://aws.amazon.com/blogs/aws/new-http-3-support-for-amazon-cloudfront/) | HTTP/3 for viewers; WebSocket over HTTP/1.1; WebSocket APIs with a 2-hour maximum. | Not documented. |
| [AWS Network Load Balancer](https://aws.amazon.com/about-aws/whats-new/2025/11/aws-network-load-balancer-quic-passthrough-mode/) | QUIC passthrough listeners (announced 2025-11-13), connection-ID stickiness, QUIC v1 only. | A load balancer, not a server: you run the WebTransport server behind it. AWS makes no WebTransport statement. |
| [Google Cloud](https://docs.cloud.google.com/load-balancing/docs/features) | HTTP/3 from clients to some load balancers; Cloud Run supports WebSockets. Passthrough network load balancers handle TCP and UDP. | Not documented for Cloud Run. Self-host behind a passthrough load balancer. |
| [Azure Front Door](https://learn.microsoft.com/en-us/azure/frontdoor/front-door-faq) | HTTP and HTTP/2 to clients; HTTP/1.1 to origin. | Not documented. |
| [Deno Deploy](https://docs.deno.com/deploy/) | Apps, frameworks, caching and cron. | Not documented. The Deno runtime has an unstable QUIC API, which is a different thing from Deploy. |
| [Fly.io](https://docs.fly.io/networking/udp-and-tcp) | UDP services on a dedicated IPv4 address; you bind to a specific address and keep packets near 1,300 bytes. | No official WebTransport statement. It supplies UDP; the server is yours. |
| [Akamai](https://techdocs.akamai.com/property-mgr/docs/http3-support) | HTTP/3 from clients to the edge. | Not documented. |

## What works in practice?

The documented building blocks are all variations on "run the server yourself":

1. **A VM, bare-metal host or container host with an open UDP port.** You need a reachable UDP port and a certificate your clients trust. The moq.dev production guide also suggests a TCP port for HTTPS or WebSocket fallback and raising Linux UDP buffer sizes.
2. **Fly.io UDP services**, within its documented constraints on addresses and packet size.
3. **A UDP- or QUIC-passthrough load balancer** such as AWS NLB or a Google Cloud passthrough network load balancer, in front of servers you run. QUIC connection IDs let a connection survive address changes, so load balancers need connection-ID-aware routing; AWS documents connection-ID stickiness for this.
4. **Managed MoQ relays** if your real goal is media distribution rather than a generic WebTransport server.

For libraries to run on those hosts, see [WebTransport client and server libraries](/guides/webtransport-client-libraries/).

## What does this mean for this site?

This site is static HTML on Cloudflare Workers static assets. It cannot answer a WebTransport handshake, and an HTTP proxy in front of a domain does not turn it into a QUIC echo service. That is why [the old echo hostnames redirect to the echo server page](/echo-server/) and why the [browser tester](/tools/webtransport-tester/) connects to servers you choose rather than to one of ours.

## History of this URL

This path previously held a WebTransport test page for a third-party serverless service; an [archived copy from February 2023](https://web.archive.org/web/20230208093159/https://webtransport.day/serverless) shows it. That service is not available here, and nothing on this site connects to it.

## How was this checked?

We opened each provider's own documentation, changelog or announcement on 2026-10-28 and recorded what it says. Some pages blocked automated fetching or returned errors; we did not work around that, and we left those claims out. Netlify's documentation did not mention WebSockets, HTTP/3 or WebTransport in the pages we reached, so it is not in the table. If you know of an official statement that corrects this page, [contact us](/contact/).

## FAQ

### Can Cloudflare Workers be a WebTransport server?

Cloudflare's Workers documentation lists WebSockets and outbound TCP sockets, but we found no WebTransport or UDP server API in its runtime or protocol pages on 2026-10-28. Cloudflare does document HTTP/3 from clients to its edge, and managed Media over QUIC relays in beta.

### Does "not documented" mean "impossible"?

No. It means we could not find a provider statement that it works. Platforms change, and a feature may exist in a changelog or preview we did not find. Check the provider's current documentation before you decide.

### What is the simplest way to host a WebTransport server?

Run a WebTransport-capable server on a virtual machine or container host that exposes a UDP port, with a trusted certificate. Fly.io documents UDP services, and AWS and Google Cloud offer load balancers that pass UDP or QUIC traffic through.

## Sources

- [Cloudflare Workers: runtime APIs](https://developers.cloudflare.com/workers/runtime-apis/)
- [Cloudflare Workers: supported protocols](https://developers.cloudflare.com/workers/reference/protocols/)
- [Cloudflare: HTTP/3 (Speed)](https://developers.cloudflare.com/speed/optimization/protocol/http3/)
- [Cloudflare Spectrum limitations](https://developers.cloudflare.com/spectrum/reference/limitations/)
- [Cloudflare Media over QUIC (MoQ)](https://developers.cloudflare.com/moq/)
- [IETF draft-ietf-webtrans-http3 (WebTransport over HTTP/3)](https://datatracker.ietf.org/doc/draft-ietf-webtrans-http3/)
- [Fastly: enabling HTTP/3](https://www.fastly.com/documentation/guides/full-site-delivery/performance/enabling-http3-for-fastly-services/)
- [Vercel: functions and WebSockets](https://vercel.com/docs/functions/websockets)
- [AWS: HTTP/3 support for Amazon CloudFront](https://aws.amazon.com/blogs/aws/new-http-3-support-for-amazon-cloudfront/)
- [AWS: Network Load Balancer QUIC passthrough mode](https://aws.amazon.com/about-aws/whats-new/2025/11/aws-network-load-balancer-quic-passthrough-mode/)
- [AWS Lambda limits](https://docs.aws.amazon.com/lambda/latest/dg/gettingstarted-limits.html)
- [Google Cloud load balancing features](https://docs.cloud.google.com/load-balancing/docs/features)
- [Google Cloud Run container contract](https://docs.cloud.google.com/run/docs/container-contract)
- [Azure Front Door FAQ](https://learn.microsoft.com/en-us/azure/frontdoor/front-door-faq)
- [Deno Deploy documentation](https://docs.deno.com/deploy/)
- [Fly.io: UDP and TCP services](https://docs.fly.io/networking/udp-and-tcp)
- [Akamai: HTTP/3 support in Property Manager](https://techdocs.akamai.com/property-mgr/docs/http3-support)
- [moq.dev: production setup](https://doc.moq.dev/setup/prod)
- [Wayback Machine: webtransport.day/serverless (8 February 2023)](https://web.archive.org/web/20230208093159/https://webtransport.day/serverless)