Check if a website serves gzip or brotli compressed responses with compression ratio and size savings display.
Gzip Compression Tester examines the response for one entered URL and reports whether its representation is sent with the HTTP gzip or br content coding. It pairs the detected coding with compressed and uncompressed byte counts, then summarizes the reduction as a ratio and size saving. The result concerns that particular resource and request, not the whole domain. A common surprise is that one site can compress an HTML document while leaving an image, API response, redirect, or very small resource uncompressed.
The entered URL selects a single response to inspect. A gzip result corresponds to the HTTP gzip content-coding token, while a Brotli result corresponds to br. If neither supported coding is reported, the result does not establish an uncompressed response: another content coding may be present, or cross-origin restrictions may prevent the browser from exposing enough response information to determine the coding.
The report places the compressed size beside the corresponding uncompressed size and turns their difference into a size saving and compression ratio. Those figures compare representations of the tested resource. They do not measure total page weight, rendering time, or the sizes of scripts, stylesheets, images, fonts, and other subresources that an HTML document may load.
Compression is negotiated and selected per response. The requested path may be tiny, already compressed, generated differently, served from another cache tier, or returned with an error or redirect. Test a compressible HTML, CSS, JavaScript, or JSON resource and make sure the status and final resource are the ones you intended to inspect.
No. The URL is handled in the browser and its response contents are not uploaded to a separate analysis service. The target website still receives the request, as it would during ordinary navigation, and network intermediaries may observe it. Cross-origin restrictions, authentication, consent screens, or bot defenses can also prevent a complete result.
The behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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