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Cairn
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For IT and managers

Straight answers for the person who has to say yes: what Cairn is, what it touches, and what it does not.

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What you need to know

Runs only on each person’s own computer.
Cairn opens at a private address on that computer (127.0.0.1) in the person’s usual browser. Nobody else on the network can reach it, and nothing is hosted anywhere.
No server and no administrator rights.
There is nothing to install on the file server. The Windows installer installs just for the user and does not ask for an administrator password.
Permissions belong to the folder.
Cairn has no accounts or log-ins. Who can read or write pages is whatever the shared folder’s own permissions allow, the same as any file on that drive.
Works offline, with no outside requests.
Fonts and scripts are built in. The only thing Cairn looks up online is a once-a-day check for a newer version, which can be turned off, and a proxy can be set. The check sends nothing about the user or their documentation.
A strict Content-Security-Policy.
The pages Cairn serves allow no inline scripts and no inline styles, which keeps the browser side tightly locked down.
Signed updates, checksums on every download.
Each download comes with a SHA-256 checksum and a minisign signature. Updates are signature-checked before they install, and the user can go back to the previous version.
The builds themselves are not code-signed.
Cairn is free and open source and does not use a paid signing certificate, so Windows SmartScreen and Mac Gatekeeper show a first-run caution. Users choose More info then Run anyway on Windows, or Open Anyway once on a Mac.
Documentation stays in plain files.
Pages are Markdown and pictures are ordinary picture files, kept in folders you already back up. Cairn adds only a small shared-docs.json and a _system folder for earlier versions and edit notes.
Open source under the MIT licence.
The code is public on GitHub, so your team can read it. Security problems can be reported privately through the project’s security page.

Will it work on our shared drive?

Cairn coordinates editors with small lock files kept in the folder itself, so it depends on the storage behaving like a real file system.

Safe for several editors

  • Local disks (NTFS, APFS, ext4)
  • Network shares using SMB2 or SMB3, which is most office file servers

Not safe for several editors

  • Folders kept in OneDrive, Dropbox or Google Drive
  • Some NAS devices (Cairn warns you when it opens a folder it cannot trust)

Cairn only knows about edits made in Cairn. If someone changes a file in another program, Cairn notices when the next person publishes and shows both versions side by side instead of overwriting.

Computers it runs on

  • Windows 10 or 11, 64-bit
  • Mac with macOS 11 or newer (Apple silicon or Intel)
  • 64-bit Linux (x86_64)

Questions your team still has? Read the questions and answers, look at the code on GitHub, or ask there.