h2check

Gzip and brotli compression test

Requests a URL twice, once asking for no compression and once asking for gzip and brotli, and reports the bytes saved.

Checker offline. Follow the manual steps below, they give the same answer.

What it checks

  • content-encoding on the compressed response.
  • Bytes transferred with and without compression, and the ratio between them.
  • Whether brotli is offered as well as gzip.
  • Vary: Accept-Encoding, without which a shared cache can serve a compressed body to a client that cannot read it.
  • Whether the response was compressed at all, which many servers skip below a size threshold.

What is not stored

This checker runs on a server, and the server is not deployed yet, so the form above is disabled. The manual steps on the procedures below return the same answer from your own machine, and they are what the checker automates.

Limits

  • Only the document at the URL you give is measured, not the scripts and styles it loads.
  • A server may compress for some user agents and not others.
  • Already-compressed formats such as images gain nothing, and a low ratio on them is correct behaviour.

Procedures that explain the result

Put it on your own page

Link to it with the value filled in, and the checker runs as soon as the page opens.

<a href="https://h2check.org/tools/compression/">Gzip and brotli compression test</a>