Converting formats

Converting is just compressing into a different format. Set -f, --format and imgsqz reads your source (any format sharp understands) and writes the target.

imgsqz input.png -f webp     # PNG → WebP
imgsqz input.jpg -f avif     # JPG → AVIF
imgsqz input.webp -f jpg     # WebP → JPG
imgsqz input.tiff -f png     # TIFF → PNG

Supported output formats

-f value	Extension	Best for
jpg (or jpeg)	.jpg	Photos, universal compatibility
png	.png	Graphics, transparency, lossless
webp	.webp	Modern all-rounder, great compression
avif	.avif	Smallest files for photos, modern browsers
tiff	.tiff	Archival / print workflows (LZW compressed)

Note

jpeg is accepted as an alias and normalized to jpg — the output extension is always .jpg.

Which format should I pick?

WebP — the safe default

Excellent compression, supports transparency and lossless, and is supported by every current browser. If you’re unsure, choose webp.

AVIF — the smallest

Typically beats WebP by 20–50% on photos at similar quality. Use it where your audience’s browsers support it (all modern ones do).

JPG — maximum reach

When something must open everywhere — email, legacy apps, print shops — JPG with mozjpeg is still a great choice.

PNG — graphics & transparency

Logos, icons, screenshots with text, anything needing an alpha channel and crisp edges.

Common conversions

# PNG screenshot → compact WebP
imgsqz screenshot.png -f webp -q 80

# Huge camera JPG → tiny AVIF for the web
imgsqz IMG_4821.jpg -f avif -q 50 --width 1600

# WebP back to JPG for an app that can't read WebP
imgsqz asset.webp -f jpg -q 85

# PNG with transparency → lossless WebP (keeps the alpha channel)
imgsqz icon.png -f webp --lossless

Transparency notes

WebP, AVIF and PNG all support an alpha channel, so transparency is preserved when converting between them. JPG has no transparency — converting a transparent PNG to JPG flattens the alpha (transparent areas become black/white depending on the source). If you need transparency, target webp, avif, or png.

Batch-converting a folder

Convert every PNG in a directory to WebP at once:

imgsqz *.png -f webp -q 75

Each file is written next to its source with a timestamp suffix. For predictable names or in-place replacement, see Output paths & naming and Replacing files in place.

Tip

Want to serve modern formats with a fallback? Generate both and let the browser pick with <picture>:

imgsqz hero.png -f avif -q 50 -o hero.avif --no-timestamp
imgsqz hero.png -f webp -q 75 -o hero.webp --no-timestamp
imgsqz hero.png -f jpg  -q 82 -o hero.jpg  --no-timestamp

<picture>
  <source srcset="hero.avif" type="image/avif" />
  <source srcset="hero.webp" type="image/webp" />
  <img src="hero.jpg" alt="" />
</picture>

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Next: Resizing & fit modes.