Detect HTTP/3
HTTP/3 is the third major version of the Hypertext Transfer Protocol used to exchange information on the World Wide Web.
Detection looks at response headers across 2 fingerprint rules among the site's public responses.
01
Websites using HTTP/3
Loading website list…
02
Signal classes
PluginView evaluates public page signals in these classes when identifying HTTP/3. Individual fingerprint rule bodies are proprietary and are not published.
- Response headers
03
Example public indicators for HTTP/3
Illustrative indicators derived from public catalog metadata for HTTP/3. A live scan may match additional proprietary rules beyond these examples.
- alt-svc: h3
- x-firefox-http3: h3
04
What a detection means
- Establishes
- One or more public signals on the scanned page matched a known HTTP/3 signature (2 rules) at the time of the scan.
- Does not establish
- A sitewide install of HTTP/3, an active vendor contract, exclusive use, or that HTTP/3 is still in place today.
05
How to check a site for HTTP/3
- 1. Enter the website URL in the scan form — homepage, pricing, checkout, or login pages usually expose the strongest HTTP/3 signals.
- 2. PluginView reads only public responses (response headers) and scores them against the HTTP/3 signature set (2 rules).
- 3. Review the confidence score and text explanation for HTTP/3 on the results page.
06
FAQ: detecting HTTP/3
- Can PluginView detect HTTP/3 without logging in?
- Yes. PluginView only reads publicly accessible responses when checking for HTTP/3 — typically response headers. It does not bypass authentication or paywalls.
- What category is HTTP/3?
- HTTP/3 is classified under Miscellaneous in the PluginView directory.
- How many fingerprint rules cover HTTP/3?
- This reference currently tracks 2 fingerprint rules across response headers. Individual rule bodies are proprietary and are not published.
- What public signals suggest a site uses HTTP/3?
- Illustrative public indicators for HTTP/3 include alt-svc: h3; x-firefox-http3: h3. A live scan may match additional proprietary rules beyond these examples.
