Compression Status
See whether HTTP compression is active for the tested URL instead of relying on file extensions or assumptions.
Free website compression test
GZIP Checker – Test Website Compression
Check whether a public website uses HTTP compression, read its Content-Encoding and compare measured transfer sizes for GZIP, Brotli, deflate or an uncompressed response.
Start compression test No registration required
- GZIP compression test
- Content-Encoding detection
- Brotli and deflate detection
- Measured transfer sizes
GZIP compression checker
Run a Website Compression Test
Enter a public HTTP or HTTPS URL. The checker requests an identity response and a compressed response, follows safe redirects and reads the final Content-Encoding header.
Check GZIP Compression
The GZIP checker verifies whether the final HTTP response is compressed and reports the exact Content-Encoding selected by the server. It distinguishes GZIP, Brotli, deflate and an uncompressed identity response.
HTTP Content-Encoding
Read the response header that identifies gzip, br, deflate, identity or another encoding returned by the server.
Measured Transfer Sizes
Compare measured identity and compressed transfers when the server provides responses that can be evaluated reliably.
Final Response Check
Follow validated public redirects and evaluate the final response, HTTP status, content type and Vary header.
Compression test
Website Compression Test
HTTP compression reduces suitable response content before it travels across the network. The browser decompresses the response after receiving it, so the page can use the original HTML, CSS, JavaScript or text data.
File size and transfer size are not always identical. This compression testing tool measures the transferred response bytes for an identity request and a request that advertises supported encodings. Savings are shown only when the responses can be compared reliably.
HTTP compression test
How the GZIP Checker Works
The checker uses response headers and measured transfers rather than guessing from page content or a filename.
- 01
Request the identity response
The first request asks the server for an uncompressed identity response to establish a measurable comparison where available.
- 02
Request supported compression
The second request advertises GZIP, deflate and Brotli and measures the raw response before any local decompression can change the transferred size.
- 03
Interpret Content-Encoding
The report identifies the encoding selected by the server and calculates measured transfer savings only when both responses are comparable.
GZIP and Brotli Compression
GZIP and Brotli are negotiated through Accept-Encoding and reported through Content-Encoding. The checker reads the raw transfer, so it can identify and measure Brotli without locally decoding the response.
GZIP Compression
GZIP is widely supported and remains a common choice for compressing text-based website responses.
Brotli Compression
Brotli can reduce text resources more efficiently in many cases, but the selected encoding always depends on server and client support.
Negotiated Per Request
A server can return different encodings for different clients, resources, content types or cache variants.
Website compression
Why Website Compression Matters
Smaller text responses require fewer transferred bytes, which can reduce bandwidth usage and help content arrive sooner. Compression is one technical performance measure and should be assessed together with response time, caching, images and resource delivery.
Free GZIP checker
Start compression test Test Your Website Compression Now
Check GZIP, Brotli, deflate and the final Content-Encoding without installing software.