Glossary
What is the quarantine attribute on Mac?
MarkdownWhat it is
It is an extended attribute stored with the file. Browsers, Mail and other apps set it on downloads. It records which app saved the file and when.
Why it matters on a Mac
Because of this flag, a downloaded app triggers the first-open check. When that check fails you may see that the app is damaged, even though the file is not corrupt.
How to check or change it on macOS
In Terminal, xattr -l /path/to/App.app lists attributes. xattr -cr /path/to/App.app removes all extended attributes from the app and its contents, including quarantine. Do this only for software you trust.
How Toolbox handles it
Fix App Is Damaged shows the app's signing details and then clears the quarantine flag for you after you confirm.
Frequently asked questions
Is removing the quarantine flag safe?
Only if you trust the source. It skips Gatekeeper's check for that app.
Do all files get the flag?
Files saved by apps that set it do. Files from other places, such as a USB stick, usually do not.
What does xattr -cr do?
It clears all extended attributes recursively, including quarantine.
