Compression (gzip/brotli) Check

Check whether the server applies gzip/brotli compression and the savings.

The compression check tool verifies in real time whether a server applies content compression such as gzip or brotli (br) to a given URL. Just like a browser, it sends an Accept-Encoding: gzip, br, deflateheader and then reads the response's Content-Encoding value to show which compression, if any, is in use.

Text-based assets (HTML, CSS, JavaScript, JSON, and so on) shrink dramatically once compression is enabled, improving load times and Core Web Vitals. If compression is missing, you are leaving one of the easiest, highest-impact optimizations on the table. Enter a URL to see the applied encoding alongside the Content-Type and Vary headers. To see how heavy the page is, use the page weight analyzer, and to check whether the server responds quickly, the response time test.

URLe.g. https://example.com (enter the full URL)

gzip vs brotli

gzip is the standard compression method supported by virtually every server and browser. brotli (br) is a newer algorithm from Google that typically compresses the same text 15-25% smaller than gzip. Most modern browsers support brotli over HTTPS, so a good setup serves brotli for static text assets while keeping gzip enabled for dynamic responses and older clients.

Which assets to compress

Compress: text-based assets such as HTML, CSS, JavaScript, JSON, SVG and XML
Skip: already-compressed binaries like JPEG, PNG, WebP and MP4 (recompressing wastes CPU for almost no gain)
Vary header: compressed responses should send Vary: Accept-Encoding so caches and proxies keep compressed and uncompressed variants separate.

Differences behind proxies and HTTP/2

Intermediaries such as CDNs, reverse proxies and load balancers may handle compression themselves or decompress and recompress responses, so the origin's configuration can differ from what is actually returned. Header presentation can also vary by tool under HTTP/2 and HTTP/3. This tool reports the Content-Encoding seen on the final response, so for sites behind a CDN you are looking at what the edge returned.

Frequently asked questions

Compression is enabled but it shows none.

Some servers only compress for specific User-Agent or Accept-Encoding combinations, and a CDN or proxy may strip compression in between. Check the response's Vary header and your CDN settings.

Which is better, gzip or brotli?

brotli achieves higher text compression ratios. Because brotli is mainly supported over HTTPS, the safest setup prefers brotli while keeping gzip enabled for clients that don't support it.

Should I compress images too?

Formats like JPEG, PNG, WebP and MP4 are already compressed, so applying gzip/brotli again gains almost nothing and just burns server CPU. Compress only text-based assets.

Is the address I enter sent anywhere?

The lookup runs on our server with safety checks (blocking private and internal IPs). Beyond briefly caching the result, your URL is not separately stored or shared with third parties.

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