Mobile-First Indexing: What It Means for You
Google indexes the mobile version of your site. If mobile is weaker than desktop, rankings suffer.
Read article →How it works
- Enter the full URL you want to test (for example
https://example.com). - The tool sends a request advertising
Accept-Encoding: gzip, br, just like a browser. - It reads the
Content-Encodingheader and measures the compressed transfer size. - It compares that against the decompressed size to calculate the bytes and percentage saved.
What it shows
- Compression status — whether the response is compressed at all.
- Encoding method — Gzip, Brotli (
br) or none, from the response header. - Compressed size — the actual bytes transferred over the wire.
- Uncompressed size — the original size of the resource.
- Bytes saved — the raw difference between the two.
- Percentage saved — how much smaller the transfer became.
- HTTP status — confirmation the URL responded successfully.
Common use cases
- Verifying server config — confirm compression is actually switched on.
- Diagnosing slow pages — rule out uncompressed assets as a cause of bloat.
- Post-migration checks — make sure a new host kept compression enabled.
- Quantifying savings — show stakeholders the real bandwidth gain.
Example
Run the tool on a homepage and you might see Content-Encoding: br, an uncompressed size of 142 KB shrinking to 31 KB over the wire — a 78% reduction. If the result instead reads "not compressed," that's a clear, fixable performance win.
Frequently asked questions
Is the Compression Test free?
Yes — completely free, with no signup and no limits. Test as many URLs as you like.
Is Brotli better than Gzip?
Brotli usually compresses text a little smaller than Gzip at similar speed and is supported by all modern browsers, so it's preferred when available. Either one is far better than serving uncompressed assets. See the wider picture in our page speed optimization guide.
How does this fit into a speed audit?
Compression is one piece of performance. Pair this with the Page Speed & Size Test to measure response time and page weight, and the HTTP Header Checker to inspect caching and the full set of response headers.