Is this brotli checker completely free?

Yes, you can use it as many times as you need without creating an account. There are no hidden fees or premium tiers for checking your HTTP headers.

Does it work for mobile websites?

The tool checks the server response, which is identical regardless of the client device. The server does not change the compression algorithm based on whether you are on a phone or a desktop.

Why does it say no compression when I know my site uses it?

Your server might be checking the User-Agent string and blocking automated tools. Alternatively, you might be testing a URL that redirects before the final compressed payload is served. Try testing the final destination URL directly.

What is the difference between br and gzip?

Brotli achieves a higher compression ratio for text-based assets like HTML, CSS, and JavaScript. It is slower to compress but faster to decompress. Gzip is older and universally supported, but yields larger file sizes for the same content.

Brotli Checker

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Paste a URL into this free Brotli Checker to see if a server returns compressed assets. No signup is needed. It checks HTTP headers for the br token.

How the brotli checker reads headers

You paste a URL and the tool sends an HTTP request with the Accept-Encoding header set to gzip, deflate, br. The server decides what to send back. If it supports the algorithm, it returns Content-Encoding: br. The tool parses this header and tells you the result. It also checks the actual payload to ensure the server didn't just lie about the encoding.

Brotli is defined in RFC 7932. It uses a predefined 120 kilobyte dictionary. This dictionary contains common HTTP strings and CSS keywords. That pre-shared context lets it compress text files much smaller than older methods. You get the raw headers back so you can verify the exact token. It checks the magic bytes too. If the header says br but the payload is plain text, the tool flags the mismatch.

When to run a brotli compression test

You need this when your Lighthouse audit complains about unminified or uncompressed text. Modern CDNs support it, but misconfigured origin servers often strip the headers. You might think your edge network handles it, only to find the origin is sending raw HTML, which completely defeats the purpose of setting up a global content delivery network in the first place. If you are wondering how to check if a website uses brotli, you just paste the URL. This online Brotli Checker lets you test both the edge and the origin directly.

It is also useful when migrating from gzip. You want to confirm the new configuration actually works before pushing it to production. Just remember that static assets like images and videos are already compressed. The tool will correctly report that those files do not use text-based compression. You should only test HTML, CSS, and JSON files for meaningful results.

Verifying CDN edge configurations.
Testing origin server fallback behavior.
Debugging missing Accept-Encoding tokens.

Limits of the free Brotli Checker

This tool only checks the final URL you provide. It does not crawl your entire site. If your homepage uses it but your subpages do not, you have to test them individually. It also cannot tell you the compression ratio. It just confirms the presence of the algorithm. You need a separate profiler to measure the actual byte savings.

Some servers negotiate encoding based on the user agent. If your server serves different encodings to different clients, the result might vary. The tool uses a standard desktop browser user agent. Also, if a site requires authentication or blocks automated requests, the check will fail with a connection error. You will need to test those protected endpoints manually via curl.

How to use the brotli checker

Paste the full URL of the resource you want to test into the input field.
Click the check button to send the HTTP request with the br token.
Read the result to see if the Content-Encoding header is present.
Inspect the raw response headers for detailed negotiation data.

Compression encoding headers

Here is what the response headers look like for different compression algorithms.

Algorithm	Accept-Encoding Token	Content-Encoding Value
Brotli	br	br
Gzip	gzip	gzip
Deflate	deflate	deflate
Zstandard	zstd	zstd

Frequently asked questions

Is this brotli checker completely free?: Yes, you can use it as many times as you need without creating an account. There are no hidden fees or premium tiers for checking your HTTP headers.
Does it work for mobile websites?: The tool checks the server response, which is identical regardless of the client device. The server does not change the compression algorithm based on whether you are on a phone or a desktop.
Why does it say no compression when I know my site uses it?: Your server might be checking the User-Agent string and blocking automated tools. Alternatively, you might be testing a URL that redirects before the final compressed payload is served. Try testing the final destination URL directly.
What is the difference between br and gzip?: Brotli achieves a higher compression ratio for text-based assets like HTML, CSS, and JavaScript. It is slower to compress but faster to decompress. Gzip is older and universally supported, but yields larger file sizes for the same content.