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Measure gzip and Brotli savings for a URL

harmlessImages and performancedebian, ubuntu
Adjust the values, the command updates live
user@server
for e in identity gzip br; do curl -s -o /dev/null -H "Accept-Encoding: $e" -w "$e: %{size_download} Bytes\n" https://example.com/; done

Requests the resource three times and shows the bytes actually transferred. curl does not decompress here, so the numbers reflect what goes over the wire. If all three values are the same, the server does not compress this resource.

Note: Works just as well for individual CSS and JS files. The entry on checking gzip and Brotli in the nginx category checks only the Content-Encoding header.

Also searched as

  • how much does gzip save
  • compare brotli vs gzip size
  • compressed size of a page
  • measure transfer size curl

Related one-liners

All in Images and performance

Precompress CSS, JS and SVG files with gzip and Brotli

$find /var/www/vhosts/example.com/httpdocs/wp-content/themes -type f \( -name '*.css' -o -name '*.js' -o -name '*.svg' \) -exec gzip -k -9 -f {} + -exec brotli -k -f {} +
cautionImages and performance

Check whether a website serves gzip or Brotli

$curl -s -o /dev/null -D - -H "Accept-Encoding: br, gzip" https://example.com/ | grep -i "^content-encoding"
harmlessnginx

Check Cache-Control of all CSS, JS and image files on a page

$curl -s https://example.com/ | grep -oE '(src|href)="[^"]+\.(css|js|woff2?|jpe?g|png|gif|webp|avif|svg)(\?[^"]*)?"' | cut -d'"' -f2 | sed -E 's#^//#https://#; s#^/#https://example.com/#' | grep '^http' | sort -u | while read -r a; do printf '%-45s %s\n' "$(curl -sI "$a" | grep -i '^cache-control:' | tr -d '\r')" "$a"; done
harmlessImages and performance

Check HTTP/3 support via the Alt-Svc header

$curl -sI https://example.com/ | grep -i '^alt-svc'
harmlessImages and performance

Compare the response time of a PHP page with a static file

$for u in https://example.com/ https://example.com/wp-includes/css/dist/block-library/style.min.css; do curl -o /dev/null -s -w "%{time_starttransfer}s TTFB $u\n" "$u"; done
harmlessImages and performance

Find images without a loading attribute on a page

$curl -s https://example.com/ | tr '\n' ' ' | grep -oiE '<img[^>]*>' | grep -vi 'loading='
harmlessImages and performance

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