Download Cairn
Free and open source for Windows, Mac and Linux. About ten minutes from download to your first page.
Windows, Mac and Linux · Free and open source
Version 1.0.0, released October 7, 2026. Release notes on GitHub.
Works on
- Windows 10 or 11, 64-bit
- Mac with macOS 11 or newer (Apple silicon or Intel)
- 64-bit Linux (x86_64)
The Mac and Linux versions are new in version 1.0.
All downloads
Windows
- Installer (recommended)cairn-1.0.0-setup.exe · 6.1 MB
- Zip, no installercairn-1.0.0-windows-x64.zip · 5.5 MB
Mac
- Zip for Apple silicon and Intelcairn-1.0.0-macos-universal.zip · 9.1 MB
Linux
- AppImage (recommended)cairn-1.0.0-linux-x86_64.AppImage · 5.5 MB
- Tar.gz archivecairn-1.0.0-linux-x86_64.tar.gz · 6 MB
How to install
Windows
- Download the installer (the file ending in -setup.exe) and open it. It installs Cairn just for you, so no administrator password is needed.
- If Windows says “Windows protected your PC”, choose More info, then Run anyway. (Why? See below.)
- Open Cairn from the Start menu. You can remove it later from Settings, then Apps. That never touches your documentation.
Prefer no installer? Download the zip, right-click it, choose Extract All, and keep the folder somewhere convenient.
Mac
- Download the zip and open it. Cairn appears next to it. It works on both Apple silicon and Intel Macs.
- Drag Cairn into your Applications folder. (Cairn can only update itself from there.)
- Open Cairn. The first time, your Mac says it cannot check Cairn for malicious software. Choose Done, open System Settings, then Privacy & Security, scroll down, choose Open Anyway next to the message about Cairn, and confirm. You only do this once.
Linux
- Download the AppImage and double-click it. If nothing happens, right-click it, choose Properties, then Permissions, and tick “Allow executing file as program”.
- Keep the file somewhere of your own, such as your home folder, so it can update itself.
Prefer an archive? Download the tar.gz, unpack it, and run ./cairn in a terminal.
Then start Cairn
A small window opens (a Terminal window on a Mac or Linux) and your web browser shows Cairn. It only works on your own computer, at an address starting with 127.0.0.1. Keep the small window open while you use Cairn. Closing it stops Cairn.
The first-run caution, and why it appears
Cairn is free and open source, and its downloads are not signed with a paid certificate. So Windows SmartScreen and the Mac’s Gatekeeper show a caution the first time, for any program they have not seen before.
It is a normal prompt, and you only see it once. On Windows choose More info, then Run anyway. On a Mac choose Open Anyway in System Settings, under Privacy & Security.
Want to check your download?
Every file has a .sha256 checksum and a .minisig signature next to it on the release page. Your IT person can use them to confirm the file is exactly what was published.