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HTTP compression checker

Check whether a URL is really served gzip or Brotli by reading the actual Content-Encoding and wire byte size, without auto-decompression.

A browser fetch would hide exactly what this tool reads

Nothing leaves this page until you do. A normal browser fetch decompresses on arrival and does not surface Content-Encoding, so the honest route is the proxy: it reports the coding the server actually applied and the bytes that actually crossed the wire.

One bound to know before reading a result: the proxy sends no Accept-Encoding header, so this measures the server's default behavior. Some servers compress unconditionally and show a coding here; most only compress for clients that offer gzip or Brotli, and for those the tell is the Vary row, which says the representation depends on what the client offers. A decoded-size savings figure cannot come from one capped GET, so none is claimed: the wire size is the number that is knowable. The body read stops at the proxy's size cap, and a truncated read is labeled as a floor, not a full transfer. Compression on a type that is already compressed, like PNG or MP4, is flagged as wasted: it spends CPU and can grow the payload.

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HTTP compression checker

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