Gzip and Brotli Compression Test
Check whether a URL is served compressed, which algorithm is used, and how many bytes compression saves. Free online gzip and brotli test.
This check runs from our server, not from your browser, and is rate limited. Nothing you enter is stored. Private and internal addresses are refused on purpose.
What this tool is for
Text compression is the single cheapest performance win available: one server setting, typically 60 to 80 percent off HTML, CSS and JavaScript. This requests the page twice, once asking for compression and once not, and compares what came back. This is one of the few tools here that needs a server, because the question is about the internet rather than about your data. The request is made from our server, rate limited, and nothing you enter is stored.
How to use it
- Enter a URL.
- Read whether the response was compressed and with what.
- Compare the sizes to see what compression is buying you.
Frequently asked questions
Gzip or brotli?
Brotli is smaller, typically by another 15 to 20 percent on text, and is supported everywhere that matters. Serve brotli with gzip as the fallback: most servers and CDNs do both with one setting.
Should images be compressed too?
No. JPEG, PNG and WebP are already compressed, and running gzip over them wastes CPU for nothing. Compress text: HTML, CSS, JavaScript, JSON and SVG.