Batch compress images from the command line

mogrify edits in place; magick writes new files. Prefer the second until you are sure.

# Resize and compress into a new folder (safe)
mkdir -p out
magick mogrify -path out -resize 1600x1600\> -quality 80 -strip *.jpg

# The same, overwriting the originals (destructive — copy first)
magick mogrify -resize 1600x1600\> -quality 80 -strip *.jpg

The > after the dimensions means "only shrink, never enlarge", which is almost always what you want. -strip removes metadata including EXIF and colour profiles.

# macOS / Linux
for f in *.jpg; do cwebp -q 78 "$f" -o "${f%.jpg}.webp"; done

# With a resize in the same pass
for f in *.jpg; do cwebp -q 78 -resize 1600 0 "$f" -o "${f%.jpg}.webp"; done

Passing 0 for the height preserves the aspect ratio. For lossless WebP from PNG sources, use -lossless instead of -q.

for f in *.jpg; do cjpeg -quality 80 -progressive -optimize "$f" > "out/$f"; done

Typically 5–15% smaller than the same quality from a browser or standard libjpeg, and the output is an ordinary JPEG that opens everywhere. If you are building a pipeline, this is usually the encoder to use.

# Lossless PNG optimisation, in place
oxipng -o 4 --strip safe *.png

# Lossless JPEG optimisation and metadata removal, in place
jpegoptim --strip-all *.jpg

# Remove metadata only, leaving the image untouched
exiftool -all= -overwrite_original *.jpg

All three of these are genuinely lossless on the image data. ExifTool in particular is the right tool when you want the metadata gone without re-encoding the pixels at all.

ImageMagick's syntax is the same; the loop is not.

# PowerShell
Get-ChildItem *.jpg | ForEach-Object {
  magick $_.FullName -resize 1600x1600">" -quality 80 -strip "out\$($_.Name)"
}

Note the quoting around >, which PowerShell otherwise treats as redirection. WSL is often simpler if you are following examples written for a Unix shell.

For a handful of images it is slower than dropping them into a browser, and for anything containing an identity document there is no privacy argument — a local tool and a client-side browser tool are equally private.

Where it wins decisively is scale, repeatability and encoder quality: thousands of files, the exact same settings every time, and access to MozJPEG and AVIF encoders that browsers do not expose.