Free tool · no signup · runs now
Compression checker
Uncompressed HTML pays the full byte bill on every visit. Compression is a one-line server setting with the fastest payoff in performance.
Part of the Technical SEO audit & onpage SEO audit group — also included in the free full scan.
Checks this exact page only — it does not crawl the rest of your domain.
One free scan · anonymous preview · sign in to save the full report
Response compressed (br)Static example for Compression checker; run the check above for your own result.What it checks
See whether text responses are compressed or paying the full byte bill.
Content-Encoding header (gzip, brotli, deflate, zstd), response byte size.
Reads the no-JS response only, never runs JS. One fetch shared with the full scan.
What good looks like
Good looks like brotli or gzip on text responses — uncompressed HTML pays the full byte bill on every visit. No encoding fails; byte size rides along as context.
How to fix it
Enable brotli (or gzip) compression for text responses at the CDN or server.
What the full scan adds
- All 34 checks in one pass — one URL, every category, a single report.
- Evidence on every row: the values found, why it fails, the fix, and a deep link per check.
- Your score against the global distribution — see where you stand.
- Sign in and the report is kept for 1 year; anonymous reports expire after 7 days.
Official source: MDN, Content-Encoding · Rule: compression v1 · checker library
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Frequently asked questions
Is the Compression checker free?
Yes — one free run without an account, with an anonymous preview. Sign in to save the full report and keep the evidence.
How often should I run it?
After every deploy that touches routing, templates or the checked file — and after each Google core update, to confirm nothing regressed.
Does the check run JavaScript?
No — it reads the no-JS response only, exactly what a crawler or AI agent sees when it fetches the URL.
How is this different from a full audit?
This page runs one check with its full criteria and fix notes. The free full scan runs every category at once and keeps the evidence per URL — use it once you know which checks matter.
How do I check gzip or brotli compression?
Read the Content-Encoding response header for the page and its text assets. This compression checker fetches the URL and reports the encoding and byte size; if the header is missing, the response is being sent uncompressed.
Should I enable brotli or gzip?
Enable brotli where the CDN or server supports it and keep gzip as the fallback. Both are negotiated through Accept-Encoding, so browsers receive whichever they advertise; brotli usually produces the smaller text payload.