How to Fix Apple Software That Has an Invalid Signature

By Stephen Lilley

Updated September 28, 2017

If an Apple computer program has an "invalid signature," your operating system will not allow it to load and you won't be able to use it. This can happen as a result of some error that occurred during the program's installation. If you want to fix Apple software that has an invalid signature, you'll need to first uninstall the program from your computer and then reinstall it.

Click on the icon for the Apple computer program that is giving you the "invalid signature" error message. Then drag that icon to the Trash icon. This will uninstall it from your computer.

Insert the installation disc that you used to install the Apple computer program on your machine into your CD-ROM or DVD-ROM drive.

Click "Install" when the Apple computer program's installation utility opens. This will reinstall the program on your machine. The "invalid signature" error message should now be gone when you next try to access the program.


If you initially installed your Apple computer program from a file you downloaded from the Internet, simply open the "Safari" web browser and re-download the file. Then click on the file's icon to open it's installation program. Then click "Next" to reinstall the program and fix the "invalid signature" error messages.