Safari crashing after updating to OS Sierra

Might be a corrupt .plist.

Do a backup, preferably 2 backups on 2 separate drives.

Quit the application.

Go to Finder and select your user/home folder. With that Finder window as the front window, either select Finder/View/Show View options or go command - J. When the View options opens, check ’Show Library Folder’. That should make your user library folder visible in your user/home folder. Select Library. Then go to Preferences/com.apple.Safari.plist. Move the .plist to your desktop.

Restart the computer, open the application, and test. If it works okay, delete the plist from the desktop.

If the application is the same, return the .plist to where you got it from, overwriting the newer one.

Thanks to leonie for some information contained in this.

I'm among the multitudes who have reported this issue today. I tried the suggested workaround but, like others, the problem goes away for a short while after restart and then comes back.

A suggestion from Macworld is to change Safari to Private browsing. However, Safari itself is not crashing for me; just the safe browsing service. For me, the issue specific thread that's crashing is com.apple.SafeBrowsing.Backend.Google.DatabaseUpdater.

Hi,

A Safe Mode boot deletes system caches that can help after upgrading to a new OS.

To start up in safe mode:

1. Start or restart your Mac, then immediately press and hold the Shift key. The white Apple logo appears on your display. If you don't see the Apple logo, learn what to do.
2. Release the shift key when you see the login window. If your startup disk is encrypted with FileVault, you might be asked to log in twice: once to unlock the startup disk, and again to log in to the Finder.

To leave safe mode, restart your Mac without pressing any keys during startup.

Then try Safari.

If that didn't help, follow the troubleshooting steps here > If Safari is slow, stops responding, quits unexpectedly, or has other issues - Apple Support