Compression Checker
Check whether a response is compressed, and measure exactly how much is being wasted if not.
About this tool
Checks whether a URL is served compressed, and if it is not, compresses the body here to show precisely what it would have saved.
Text compresses by roughly seventy per cent. Enabling it is a line of server configuration and no ongoing cost, which makes an uncompressed HTML document the largest cheap win available on most sites. It is also completely invisible — the page works, it is simply three times larger than it needs to be, and nothing anywhere says so.
**The saving shown is measured, not estimated.** The body is actually compressed with gzip and, where the server supports it, deflate, and the resulting byte counts are reported. A figure derived from a typical ratio would be a guess wearing the clothes of a measurement.
Brotli is negotiated with the server rather than tested locally, because PHP cannot produce it without an extension most hosts do not have.
Common questions
Should I use gzip or Brotli?
Brotli where you can — it produces files roughly 15 to 20 per cent smaller than gzip on text. Serve gzip alongside it as a fallback; every browser supports gzip and configuring both is normal.
Which files should be compressed?
Anything text: HTML, CSS, JavaScript, JSON, SVG, XML. Not JPEG, PNG, WebP, MP4 or fonts in WOFF2 — those are already compressed, and running them through gzip costs CPU and saves nothing.
Why is my page not compressed even though I enabled it?
Usually a minimum size threshold, a content type not in the server's list, or a proxy stripping the Accept-Encoding header before the request arrives. The response headers here show what actually happened.
Is there a security reason not to compress?
The BREACH attack exploits compression on responses that mix a secret with attacker-controlled input. It affects specific cases, not ordinary pages, and the mitigation is masking the secret rather than disabling compression everywhere.