Comment utiliser : Website Compression Test
- Enter a page URL or just a domain and click Test compression.
- Read the verdict: Brotli, gzip, Zstandard or no compression.
- Compare transferred bytes per
Accept-Encodingvalue and see how small the page could be with gzip 9 or Brotli 11. - Check the CSS and JavaScript list for files that are sent uncompressed, then follow the recommendations.
What does HTTP compression do?
Browsers send an Accept-Encoding header listing the compression formats they understand — today usually gzip, deflate, br, zstd. A correctly configured server picks one, compresses the response and labels it with Content-Encoding. For text such as HTML, CSS, JavaScript, JSON and SVG this typically cuts transfer size by 60–80 %, which directly improves load time, Largest Contentful Paint and mobile data usage.
What this test checks
- Each encoding separately: the page is requested with
identity,br,gzip,zstdand a browser-like combined header, and the real transferred bytes are measured. - Potential savings: the uncompressed page is compressed on our server with gzip 6, gzip 9, Brotli 5 and Brotli 11, so you can see what you are leaving on the table.
- Linked CSS and JavaScript: up to 12 stylesheets and scripts from the page are checked, because it is common for HTML to be compressed while static files are not.
- Vary header:
Vary: Accept-Encodingtells caches to store compressed and uncompressed versions separately.
Enabling compression
| Server | Gzip | Brotli |
|---|---|---|
| Nginx | gzip on; gzip_types text/css application/javascript application/json image/svg+xml; | ngx_brotli module: brotli on; brotli_types …; |
| Apache | mod_deflate: AddOutputFilterByType DEFLATE text/html text/css application/javascript | mod_brotli: AddOutputFilterByType BROTLI_COMPRESS … |
| Node / Express | compression middleware | Pre-compressed .br files or a CDN |
| Cloudflare, Vercel, Netlify | Automatic for text content types | |
What not to compress
JPEG, PNG, WebP, AVIF, video, fonts in WOFF2 and ZIP files are already compressed — running gzip over them wastes CPU and can even make them larger. Compress text formats only. For the files themselves, minify first (JavaScript, HTML, CSS), then let the server compress them.
Our requests identify as DevPackBot and fetch only the URL you enter plus its linked CSS and JS files. Sites behind bot protection may block the test.
Aussi recherché comme : gzip test, check gzip compression, brotli test, is gzip enabled, http compression test, check brotli, content-encoding checker, zstd test.
Outils complémentaires : Website Compression Test
- Page Speed Test — Run Google Lighthouse on any URL for mobile or desktop.
- HTTP Header Checker — Fetch any URL and see exactly what the server sends back — status code, redirect chain and every response header, with a plain-English explanation of the ones that matter for SEO, caching and security.
- Brotli Compress & Decompress — Compress text or files with Brotli at any quality from 0 to 11, decompress .br data, and compare the result against gzip — all locally in your browser.
- Gzip Compress & Decompress — Compress text or any file with gzip, zlib or raw deflate — or paste Base64 / open a .gz file to decompress it.
Questions fréquentes
How do I check if gzip is enabled on my website?
gzip shows “Gzip” as the server’s encoding and a much smaller byte count than identity, gzip is enabled.Is Brotli better than gzip for websites?
What is Zstandard (zstd)?
Content-Encoding: zstd, and some CDNs have started serving it. Brotli and gzip remain the most widely deployed.