pXL Compare Support

How do I install pXL Compare?

Download the ZIP file, open it to unzip, and drag pXL Compare into your Applications folder. The app is signed and notarized by Apple, so it opens like any other Mac app.

The first time it opens, the Required Tools window shows which encoders are installed. You can close it and come back to it any time from the Help menu.

How do I get updates?

From version 1.0.3, pXL Compare updates itself. The second time you open it, it asks whether to check for updates automatically. You can also choose pXL Compare → Check for Updates… at any time. Updates are signed, so pXL Compare only installs versions that come from us.

Version 1.0.2 and earlier can’t update themselves. Download the latest version from this page once, replace the old app in your Applications folder, and future updates arrive on their own.

What do I need to run pXL Compare?

A Mac running macOS Tahoe 26.6 or later. JPEG (System) and HEIF (System) work right away, and JPEGli and jixel are included with the app. The other seven encoders need free command-line tools, which you install once.

How do I install the encoders?

Install Homebrew from brew.sh if you don’t have it, then run this in Terminal:

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

JPEGli and jixel are included with pXL Compare, so there’s nothing else to install. jixel uses the JPEG XL decoder, which the command above installs.

A panel says a tool is missing. What do I do?

Open Required Tools (⌥⌘R, or from the toolbar or Help menu). It lists every encoder, shows whether it’s installed, and gives you a command you can copy. After installing, click Re-check. You don’t need to restart the app.

My tools are installed somewhere unusual. Can pXL Compare find them?

Yes. pXL Compare looks in ~/bin, /opt/homebrew/bin, /usr/local/bin and the standard system folders. To add another folder, such as /opt/local/bin, open Settings and add it under Custom Tool Directories. Those folders are searched first.

Why are the System encoders so much faster?

JPEG (System) and HEIF (System) run inside the app. The other encoders start a separate program and read and write files for every run, and that overhead is included in their speed. Compare speeds within each group, especially on small images.

Why does libjpeg-turbo score lower on some images?

libjpeg-turbo only accepts 8-bit sRGB, so wide-color images are converted to sRGB before encoding. Its SSIMULACRA2 score can come out lower than codecs that receive the full 16-bit source.

Does pXL Compare upload my images?

No. Everything runs on your Mac. Working files go in /tmp/CompressionComparison and are deleted automatically: as soon as they’re replaced, when you quit, or after 24 hours at the latest.

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