How to Suppress Repetition of Warnings That an Application Was Downloaded From the Internet on Mac OS X?

On Mac OS X, when I run Firefox (and Thunderbird, and ...) which I downloaded from Mozilla, the OS pops up a warning that the file was downloaded over the internet, giving the date on which it was downloaded. I have no problem with that warning on the first time I use a downloaded application - but the repeated warnings are a nuisance.

Is there a way to suppress that dialogue box?

Is there a way to avoid it appearing in the first place? (Some applications I download from a corporate intranet - those don't produce the equivalent warning; any idea what the criteria are for when the warning is generated?)

Solution 1:

To remove the quarantine alert you can run the following command in Terminal:

xattr -d com.apple.quarantine /PATH/TO/APPLICATION

You may need to run this is an administrator depending on the permissions on the resulting application (as you said you don't run as administrator). If the application has permissions set that you can't remove the metadata with your user account it explains why it comes up every time. You can either run it as an administrator on your computer or run the command above as an administrator. (Use su admin_name if necessary)

Solution 2:

To stop this from happening in the future, go to Terminal and type this (hitting Return afterwards):

defaults write com.apple.LaunchServices LSQuarantine -bool NO

Source: MacWorld

Or — simpler yet — download Secrets and search for “quarantine.”