Install Impasto on macOS

Download the disk image for your Mac from the releases page:

Not sure which you have? Apple menu > About This Mac shows the chip. If it says Apple M…, take the arm64 image.

Open the .dmg and drag Impasto onto the Applications shortcut in the same window. Eject the disk image afterwards.

The package bundles the GTK and libadwaita libraries it needs, so you do not have to install GTK yourself. It does need the .NET 10 runtime, which the package also carries.

Getting past the Gatekeeper warning

The macOS builds are not signed with an Apple Developer ID, so macOS refuses to open them normally the first time. You get one of these:

• “Impasto” cannot be opened because the developer cannot be verified.
• “Impasto” is damaged and can’t be opened. You should move it to the Trash. — for an unsigned build that arrived through a quarantine flag this is usually just Gatekeeper’s wording, not a corrupted download; the quarantine fix below is what clears it.

To allow it, use one of these.

macOS 14 and earlier — Control-click Open:

1. Open Finder and go to the Applications folder.
2. Hold Control and click the Impasto icon, then choose Open. (Or right-click and choose Open.)
3. Click Open in the dialog, which now offers an Open button instead of only Cancel.

This exemption is remembered, so Impasto opens normally from then on.

macOS 15 and later — Privacy & Security. Sequoia removed the Control-click bypass for apps that are unsigned or not notarized, so that route no longer offers Open:

1. Double-click Impasto once, and dismiss the warning.
2. Open System Settings > Privacy & Security and scroll to the Security section.
3. Next to the message about Impasto being blocked, click Open Anyway.
4. Authenticate, then confirm with Open.

The Open Anyway button only appears for about an hour after the launch attempt, so do steps 1 and 2 close together. If it is missing, move the application out of Downloads into Applications, dismiss the warning again, and reopen the pane.

Either version — clear the quarantine flag. This is the equivalent of the Control-click bypass and works on both:

xattr -dr com.apple.quarantine /Applications/Impasto.app

Then open the app normally. You only need this once per copy, and it does not require changing any system setting.

One caveat: if the dialog says “Impasto” will damage your computer rather than cannot be opened, stop. That wording means the download is corrupted or has been modified, and the fix is to download the image again from the releases page. Do not disable Gatekeeper system-wide to run Impasto.

Uninstalling

Drag Impasto from Applications to the Trash. Settings, keyboard shortcuts, and the recent-file list stay behind in ~/.config/Impasto; delete that folder to remove them too.

Building from source

Install .NET 10 and the GTK dependencies from Homebrew:

brew install dotnet-sdk libadwaita adwaita-icon-theme gettext webp-pixbuf-loader

Then set the library path so the GTK libraries can be found, or the application fails at startup with a library-loading error:

# Apple Silicon
export DYLD_LIBRARY_PATH=/opt/homebrew/lib
# Intel
export DYLD_LIBRARY_PATH=/usr/local/lib

dotnet build
dotnet run --project Impasto

Note that DYLD_LIBRARY_PATH has to be set in the same shell that runs the application. As an alternative, installer/macos/build_installer.sh patches the search path into the packaged application itself, which is how the release images work without the environment variable.