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Gzip / Brotli Compression Test

Fetch a URL from our server and report the Content-Encoding header it returns, so you can see whether the response arrived gzip or brotli compressed.

How to use this tool

  1. 1

    Paste the full URL you want to check, including the https:// scheme.

  2. 2

    Submit the form to have our server request that URL.

  3. 3

    Read the result card: it shows the Content-Encoding value (such as gzip or br) and whether compression was detected.

  4. 4

    Adjust your server configuration if the card reports no compression, then re-run the check.

What does this compression test actually check?

When a browser requests a page, it sends an Accept-Encoding header advertising which compression algorithms it supports, and the server may compress the response and announce the algorithm it chose in the Content-Encoding response header. The two common values are gzip (DEFLATE, defined in RFC 1952, supported everywhere) and br (Brotli, RFC 7932, usually a few percent smaller than gzip on text). This tool makes a single server-side request to the URL you provide and inspects only that Content-Encoding header on the response. If the header is present with a value like gzip or br, it reports the response as compressed; if the header is absent or empty, it reports no compression detected. It does not measure the actual byte savings, does not test multiple Accept-Encoding combinations, does not crawl sub-resources like your CSS and JavaScript files, and does not evaluate compression level or quality. Treat it as a fast yes/no signal for one URL. Because the request comes from our server rather than your browser, a CDN may route it differently than it routes your visitors, and some origins vary compression by user agent or path.

Common use cases

  • Confirm that a newly deployed Nginx or Apache config is actually emitting gzip or brotli on your homepage.

  • Verify a CDN such as Cloudflare or Fastly is compressing HTML responses at the edge.

  • Spot-check an API endpoint that returns large JSON to see whether it is being compressed in transit.

  • Diagnose a slow page by ruling compression in or out before digging into other performance causes.

  • Check whether a specific path (not just the root) is served compressed when rules differ per route.

  • Demonstrate to a client or teammate, with a shareable result, that their pages are or are not compressed.

Frequently asked questions

Does this tool upload or store the URL I enter?▼
The URL is sent to our server only to perform the fetch and read the Content-Encoding header. We do not store the page contents; the request is made on your behalf and the result is returned to your browser.
Why does it report no compression when my browser shows gzip?▼
The check runs from our server, not your browser. A CDN or origin may negotiate compression differently for our request, vary it by User-Agent, or only compress above a size threshold. Confirm with your browser DevTools Network tab as the source of truth.
What is the difference between gzip and br in the result?▼
gzip is the DEFLATE-based format from RFC 1952 supported by virtually every client. br is Brotli (RFC 7932), which typically produces slightly smaller text payloads. Either value means the response was compressed; the server picks one based on what the client advertises.
Does it test my CSS, JS, and image files too?▼
No. It checks only the single URL you submit. To verify sub-resources, run the test on each file URL individually. Already-compressed binaries like JPEG, PNG, and WebP gain little from gzip or brotli, so those are usually served uncompressed by design.
Does a compressed result tell me how much bandwidth I am saving?▼
No. This tool only reports whether the Content-Encoding header indicates compression. It does not download the uncompressed version or compute a ratio. For byte-level savings, use a tool that compares compressed and uncompressed sizes.
Why do I need to include https:// in the URL?▼
The server needs a complete, well-formed address to make the request. Omitting the scheme can cause the fetch to fail or resolve unexpectedly, so paste the full URL exactly as it appears in the address bar.

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