Convert an image to WebP on Mac

You’re optimising a website and your Lighthouse audit is yelling at you about image formats. WebP is the answer for most photos and graphics — 25–35% smaller than JPEG or PNG at the same visual quality, with universal browser support. The question is how to get your existing JPEGs and PNGs into WebP without buying yet another tool.

Why WebP

• 25–35% smaller files than JPEG at matched quality.
• Supports both lossy and lossless modes.
• Transparency (unlike JPEG).
• Animation (unlike PNG).
• Supported in every modern browser (Chrome, Safari 14+, Firefox, Edge).

The main downside: design tools and CMS upload forms sometimes still want JPEG or PNG.

The native way: sips

macOS Sonoma and later include WebP support in sips. One file:

sips -s format webp -s formatOptions 80 photo.jpg --out photo.webp

A folder:

mkdir webp
for f in *.jpg *.png; do
  sips -s format webp -s formatOptions 80 "$f" --out "webp/${f%.*}.webp"
done

Quality goes 0–100; 75–85 is the typical web range.

The magick way

If your sips is too old or you want more control:

brew install imagemagick
magick photo.jpg -quality 80 photo.webp

Add -define webp:lossless=true for lossless mode.

The faster way

Drag a folder of images into Melt, set output to WebP, set quality, click Compress. You see the savings file by file, and you can resize at the same time — useful when you’re prepping responsive image sets. Download Melt.

Batch convert to WebP in Melt

1. Open Melt.
2. Drag your images (JPEG, PNG, or mixed) in.
3. Set output format to WebP.
4. Pick quality — 80 is a good default for web.
5. Optionally enable resize if you're generating responsive sizes.
6. Click Compress.

Lossy vs lossless WebP

• Lossy WebP for photos and anything with smooth gradients. Smaller files, quality similar to JPEG at 85.
• Lossless WebP for screenshots, logos, anything with text or sharp edges. Smaller than PNG, lossless.

Most converters default to lossy. Switch explicitly if you need lossless.

What you lose, what you keep

Going JPEG → WebP is a re-encode, which means a small amount of extra quality loss on top of what’s already in the JPEG. Going PNG → lossless WebP is genuinely lossless. EXIF data is preserved by default in sips and Melt; strip it if you’re publishing the images publicly. Keep your original masters and serve WebP from a separate folder.