By definition they are neither. By practice any Glock pistol is single action, pulling the trigger releases the striker and nothing else. The act of cocking must be done manually by the user when initially loaded (racking the slide or slightly pulling back on the slide to the striker), and the act of cocking is automatic after that. If they were double action, every pull of the trigger would pull back and release the striker, which doesn't happen. When a Glock isn't cocked, pulling the trigger does nothing, making a Glock trigger SA.

no it is a striker fire gun which is not really a single action or a double action in a single action gun the trigger releases the cocked hammer the round fires and the action of the gun recockes it again for the next shot in a Double action the hammer starts in a down position and the trigger pull brings the hammer back and releases it to fire the gun a striker fired gun (like this one) does not have a hammer but has a firing pin that is under tension and the trigger releases the firing pin to strike the primer the gun fires and the action cycles resetting the firing pin to be ready for the next shot

Hi Cleve and welcome. Glocks are all Striker Fired Single Action Handguns. Cheers, stay safe and enjoy!

All single action.