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Website and domain checks

Brotli compression test

Ask a public resource for br content encoding and check what the response really says.

  • Accept-Encoding: br
  • Content-Encoding check
  • Vary header

Free, no sign-up. Lookups and results are not saved by this site.

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Brotli compression

Brotli is a compression format that often makes text files smaller than gzip. This test asks for Brotli and checks whether the response says it was sent that way.

Technical references: Content-Encoding header reference (opens in a new tab) and Brotli specification (RFC 7932) (opens in a new tab).

What you can do

  • A request that asks for br encoding

  • The Content-Encoding of the GET response

  • Content-Type and Vary context

  • A small sample of the body that is never kept

  • A result for one resource, with no invented savings

How to use it

  1. Enter the address

    Enter the public address of a page or file, without a username, password or other private details.

  2. Run the test

    Start the test. A quick Cloudflare security check runs first, then this site checks the address and its redirects before connecting.

  3. Read the result

    Read the result, the evidence and the limits. If you change a server or CDN setting, run the test again.

How the Brotli test works

Brotli can make text files such as HTML, CSS and JavaScript smaller. This test sends a GET request with Accept-Encoding: br and checks the encoding, content type and status the server sends back, and that the response is not empty.

Know the limits

A successful response that declares br is evidence for this one request, not for every page or browser. Small files, images and files that are already compressed may not use Brotli. The body is capped and thrown away without being decompressed, so this is not an integrity check or a measure of the saving. Error pages, empty responses and redirects give no answer either way.

Frequently asked questions

What does a successful Brotli result mean?

The page you entered returned a successful, non-empty response with br in its Content-Encoding header after the checker asked for Brotli. It does not prove that every file on the site uses Brotli.

Why might Brotli not be observed?

Compression can depend on the file type, its size, CDN settings, cache state and the headers the visitor sends. Try an ordinary HTML, CSS or JavaScript file that you are allowed to check.

Does this calculate compression savings?

No. The checker does not fetch an uncompressed copy to compare. It reports a sample of the encoded body and does not invent an original size or a savings percentage.

Is the whole compressed stream validated?

No. The body is not decompressed or kept, and large bodies are only sampled up to a limit. The result reports the content encoding that was seen, not a full integrity check.

Are these results for my origin server or my CDN?

The checker connects to the public URL. A CDN, reverse proxy or load balancer may answer instead, so the result does not show how your origin server itself is set up.

What is sent when I run a test?

Your URL and a fresh Cloudflare Turnstile response are sent to this site. After the security check, our server makes a few limited public requests. Page contents and cookies are not returned or saved.

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