MIR Assertions for GIMP BETA

Sign the images you export with your issuer identity, right from GIMP. MIR records who asserted what about a file. It never judges whether the assertion is true.

Download for GIMP 3

Free. Requires GIMP 3.0 or later and an approved issuer account.

SHA-256

Your key stays yoursGIMP makes its own signing key. Only the public half is ever sent to MIR.

Signs the real fileWhat gets asserted is the exact file you exported, byte for byte.

No dependenciesTwo small Python files. Nothing else to install.

1. Install

Download and unzip it. You get a folder called mir-assert.
Press Win + R, paste %APPDATA%\GIMP\3.0\plug-ins (use 3.2 if that's your GIMP version), and press Enter.
Move the whole mir-assert folder into that window.
Restart GIMP.

Download it. Safari unzips it for you into a folder called mir-assert.
In Finder, choose Go > Go to Folder... and paste ~/Library/Application Support/GIMP/3.0/plug-ins (use 3.2 if that's your GIMP version).
Move the whole mir-assert folder into it.
Restart GIMP.

Works for the Flatpak and for distro packages:

unzip mir-assert-gimp-*.zip -d ~/.config/GIMP/3.0/plug-ins/ (use 3.2 if that's your GIMP version)
Restart GIMP.

If you unzip it some other way, make sure mir-assert/mir-assert.py is executable (chmod +x).

Not sure where the folder is? In GIMP, open Edit > Preferences > Folders > Plug-ins. It lists the plug-in folders, and the button next to each one opens it for you. Put mir-assert in the one inside your personal folder.

After restarting, you should see File > MIR Assertions in the menu.

2. Connect your issuer account

In GIMP, choose File > MIR Assertions > Account... and click Connect...
GIMP shows a short code and opens the approval page in your browser.
Sign in to the Issuer Portal, check that the key on the page matches the one GIMP shows, and click Confirm and connect.

You do this once per computer. No issuer account yet? Apply here.

3. Assert what you export

Export your image as usual (File > Export As...).
Choose File > MIR Assertions > Assert Exported File..., pick what you're asserting (usually Issued by me), and click Assert.
You get a link to the file's public verification page.

Export and Assert does both steps at once, using your last export settings. Give it a keyboard shortcut under Edit > Keyboard Shortcuts.

The free tier includes one assertion per week. Subscribe for unlimited, or use Account... > Subscribe in GIMP.

Good to know

What's signed is the exported file, not your GIMP project. If you export again with different settings, that's a new file and it needs its own assertion.
Where your key lives: in your system keychain where GIMP can reach it. Otherwise it's in a private file in GIMP's settings folder that only your user account can read.
Lost or replaced a computer? Disconnect it from the Issuer Portal. That revokes its key immediately.
Uninstall: choose Account... > Disconnect, then delete the mir-assert folder.
Menu missing after a restart? Check that the folder structure is plug-ins/mir-assert/mir-assert.py (not plug-ins/mir-assert/mir-assert/...), and on macOS and Linux that the file is executable.

Building a plug-in for another app? The API docs cover the connect-and-sign flow.

Wilber, the GIMP mascot, by Aryeom Han, after the original by Tuomas Kuosmanen, used under CC BY-SA 4.0. Our preview image adapts it and is shared under the same license. This plug-in is independent and not affiliated with or endorsed by the GIMP project.