Images and performance

Load time drives bounce rate and rankings. Commands to shrink images and convert them to WebP or AVIF, find large media files and check compression and cache headers.

21 one-liners: 12 harmless, 5 caution, 4 destructive

images 11 find 8 curl 6 compression 4 assets 2 exiftool 2 exif 2 privacy 2 imagemagick 2 core-web-vitals 2 javascript 2 load-time 2 jpegoptim 2 jpeg 2

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

Check HTTP/3 support via the Alt-Svc header

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

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

Convert images to AVIF recursively

$find /var/www/vhosts/example.com/httpdocs/wp-content/uploads -type f \( -iname '*.jpg' -o -iname '*.jpeg' -o -iname '*.png' \) -exec sh -c 'for f; do [ -e "$f.avif" ] || avifenc -s 6 "$f" "$f.avif" >/dev/null; done' sh {} +

Convert images to WebP recursively

$find /var/www/vhosts/example.com/httpdocs/wp-content/uploads -type f \( -iname '*.jpg' -o -iname '*.jpeg' -o -iname '*.png' \) -exec sh -c 'for f; do [ -e "$f.webp" ] || cwebp -quiet -q 80 "$f" -o "$f.webp"; done' sh {} +

Find images containing GPS coordinates

$exiftool -r -ext jpg -ext jpeg -if '$gpslatitude' -p '$directory/$filename' /var/www/vhosts/example.com/httpdocs/wp-content/uploads 2>/dev/null

More power on the server

Does the optimization reach your visitors?

Faster database, more RAM, better caching: GENLOC.SEO measures whether it shows up in PageSpeed and Core Web Vitals. Free, for mobile and desktop.

by GENLOC.NETWORK, the team behind myline.de

Find images larger than a given pixel size

$find /var/www/vhosts/example.com/httpdocs/wp-content/uploads -type f \( -iname '*.jpg' -o -iname '*.jpeg' -o -iname '*.png' \) -exec identify -format '%w %h %i\n' {} + 2>/dev/null | awk -v max=2560 '$1 > max || $2 > max'

Find images without a loading attribute on a page

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

Find large images in wp-content/uploads

$find /var/www/vhosts/example.com/httpdocs/wp-content/uploads -type f \( -iname '*.jpg' -o -iname '*.jpeg' -o -iname '*.png' -o -iname '*.gif' -o -iname '*.webp' \) -size +500k -printf '%s\t%p\n' | sort -rn | head -50 | numfmt --field=1 --to=iec

Find scripts without async or defer on a page

$curl -s https://example.com/ | tr '\n' ' ' | grep -oiE '<script[^>]*src=[^>]*>' | grep -viE 'async|defer|type=.?module'

Find unminified CSS and JS files

$find /var/www/vhosts/example.com/httpdocs/wp-content -type f \( -name '*.css' -o -name '*.js' \) ! -name '*.min.*' -size +20k -exec sh -c 'echo "$(wc -l < "$1") $1"' sh {} \; | awk -v n=200 '$1 > n' | sort -rn | head -30

Find web font files and their size

$find /var/www/vhosts/example.com/httpdocs/wp-content -type f \( -iname '*.woff2' -o -iname '*.woff' -o -iname '*.ttf' -o -iname '*.otf' -o -iname '*.eot' \) -printf '%s\t%p\n' | sort -rn | head -30 | numfmt --field=1 --to=iec

Limit JPEG quality to a maximum with jpegoptim

$find /var/www/vhosts/example.com/httpdocs/wp-content/uploads -type f \( -iname '*.jpg' -o -iname '*.jpeg' \) -exec jpegoptim --strip-all --preserve --max=82 {} +

Measure gzip and Brotli savings for a URL

$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

Optimize JPEG images losslessly with jpegoptim

$find /var/www/vhosts/example.com/httpdocs/wp-content/uploads -type f \( -iname '*.jpg' -o -iname '*.jpeg' \) -exec jpegoptim --strip-all --preserve {} +

Optimize PNG images losslessly with optipng

$find /var/www/vhosts/example.com/httpdocs/wp-content/uploads -type f -iname '*.png' -exec optipng -o2 -strip all -preserve {} +

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 {} +

Remove EXIF and other metadata from images

$exiftool -r -ext jpg -ext jpeg -all= -overwrite_original /var/www/vhosts/example.com/httpdocs/wp-content/uploads

Resize large images to a maximum size with mogrify

$find /var/www/vhosts/example.com/httpdocs/wp-content/uploads -type f \( -iname '*.jpg' -o -iname '*.jpeg' -o -iname '*.png' \) -exec mogrify -resize '2560x2560>' {} +

Roughly measure the total size of a page with all assets

$wget -q -p -H -nd -e robots=off -P /tmp/page-weight https://example.com/; du -sh /tmp/page-weight; ls -lhS /tmp/page-weight | head -15

Shrink PNG images lossily with pngquant

$find /var/www/vhosts/example.com/httpdocs/wp-content/uploads -type f -iname '*.png' -exec pngquant --quality=65-85 --skip-if-larger --strip --force --ext .png {} +