HTTP/3 vs X-Clacks-Overhead

HTTP/3 is the more common of the two in our index: it runs on 22,498 websites against 68 for X-Clacks-Overhead, and 10 sites use both. Counts come from real scans, not vendor claims.

HTTP/3: 22,498
X-Clacks-Overhead: 68

HTTP/3

HTTP/3 is the third major version of the Hypertext Transfer Protocol used to exchange information on the World Wide Web.

Indexed sites: 22,498
Share of Miscellaneous: 42%

Well-known sites using it

All 22,498 sites

X-Clacks-Overhead

X-Clacks-Overhead is a non-standard HTTP header used to transmit tribute messages within server responses.

Indexed sites: 68
Share of Miscellaneous: 0%

Well-known sites using it

All 68 sites

Used together

10 sites run both HTTP/3 and X-Clacks-Overhead. That is 15% of the sites using X-Clacks-Overhead, the smaller of the two.

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Want to know which one a particular site uses? Look it up and see its whole stack, or compare two sites side by side.