What Is an HTTP/3 Test?
HTTP/3 Test checks whether a website supports HTTP/3, the modern HTTP protocol version that runs over QUIC.
HTTP/3 aims to improve connection setup and reduce some network-level delays, especially on unreliable mobile or long-distance connections. It is commonly enabled through a CDN, load balancer, or web server that supports QUIC.
What the Tool Checks
| Result | What It Means |
|---|---|
| HTTP/3 supported | The target reports HTTP/3 availability. Compatible browsers may negotiate H3 over QUIC. |
| HTTP/3 versions | When returned by the API, supported H3 version tokens such as h3 or draft variants are shown as chips. |
| HTTP/3 not detected | The target did not report HTTP/3 support in the Loadtime API protocol data. |
| Protocol context | HTTP/1.1 and HTTP/2 are shown only as context from the same protocol response. |
If HTTP/3 is not detected, check your CDN, reverse proxy, load balancer, or web server configuration. HTTP/3 usually requires QUIC over UDP, so firewall and edge-network settings matter as much as application server configuration.
Cloudflare users can refer to this guide to enable HTTP/3.
Frequently Asked Questions
HTTP/3 is the newest major HTTP protocol version. It runs over QUIC instead of TCP, which can improve connection setup and resilience on lossy networks.
HTTP/2 improves request multiplexing over TCP. HTTP/3 keeps many HTTP/2 ideas but moves transport to QUIC, reducing some TCP head-of-line blocking behavior.
HTTP/3 usually needs CDN, load balancer, or server support for QUIC over UDP. Firewalls, hosting limits, or disabled CDN settings can prevent it from being available.