Brotli
Brotli is widely used for compressible web assets over HTTPS and can reduce transfer size compared with uncompressed responses.
Website + performance
Check whether the server compresses the response.
Request the page with br and gzip accepted and inspect the encoding the server actually returns.
Result
Diagnostic result
gzip
gzip remains broadly compatible and is a useful fallback when Brotli is not selected.
Cache variation
When compression varies by Accept-Encoding, caches commonly use Vary: Accept-Encoding or equivalent cache-key behavior.
No fake savings estimate
The checker reports the negotiated encoding; it does not invent a compression ratio from a small bounded body sample.