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.
Need this at scale? Try the Loadtime API.
Measure TTFB, DNS lookup, and connection timing programmatically — same engine as this tool.
curl -X POST https://api.geekflare.com/loadtime \
-H "x-api-key: YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{"url":"https://example.com"}'