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pXL Compare

See exactly what JPEG XL, AVIF, WebP and JPEG do to your image, side by side and pixel for pixel.

Download for Mac

Free · Version 1.02 · Requires macOS Tahoe 26.4 or later · Coming soon to the Mac App Store

pXL Compare showing a dahlia photo split into four quadrants encoded as JPEG XL, AVIF, WebP and JPEGli. Each codec’s panel lists its settings, file size, savings, encode and decode speed, and SSIMULACRA2 score.

What it does

Four-way split view

Encode one image with up to four codecs and see the decoded results as aligned quadrants. Drag to move the split, hold Space to see the original, and zoom to 800% to pixel peep.

See every difference

Hold Shift to show an amplified difference map. Black pixels are identical, brighter pixels differ more, and the color shows which channels changed. Boost the gain up to 32×.

Numbers you can compare

Each panel reports encoded file size, savings against the original, bits per pixel, encode and decode speed, and a SSIMULACRA2 quality score.

Hit a quality target

Target Score mode searches each codec for the smallest file near the SSIMULACRA2 score you choose, so you compare formats at equal quality instead of equal settings.

Every control, explained

Tune distance, quality, effort, chroma subsampling, bit depth, progressive and lossless modes. Each control explains the encoder option it changes, and the command console shows the exact commands that ran.

Lossless JPEG transcoding to JPEG XL

Transcode an existing JPEG as JPEG XL without losing a single pixel, and see how much smaller it gets. Export any result to keep the encoded file.

Ten encoders, one window

Apple’s built-in encoders work as soon as you open the app. The rest use the free, open-source command-line encoders, which you install once with Homebrew. The Required Tools window lists what’s installed and gives you the command for anything missing.

brew install jpeg-xl libavif webp libheif jpeg-turbo exiftool

JPEGli is built from source rather than installed with Homebrew, and JPEG 2000 needs a libheif build that includes its OpenJPEG plugin.

Built into macOS

  • JPEG (System)
  • HEIF (System)

With free open-source tools

  • JPEG XL
  • AVIF
  • AVIF (libheif)
  • WebP
  • JPEGli
  • HEIF (libheif)
  • JPEG 2000 (libheif)
  • JPEG (libjpeg-turbo)

Need help getting set up? Read the pXL Compare support page.

Its companion app

  • pXL Crunch

    Coming soon

    A Mac photo converter for batches of images, with Finder quick actions, resizing, and quality targets. Built on the same encoding engine as pXL Compare.