The "safe action" is a firing pin lock system which Glock

Glock

Glock Ges.m.b.H. is a weapons manufacturer headquartered in Deutsch-Wagram, Austria, named after its founder, Gaston Glock...

 developed to be used in the vast majority of their pistols. The action is very similar to the quick action used by Walther and other pistol manufacturers.
The system consists of one external and two internal safeties

Safety (firearms)

In firearms, a safety or safety catch is a mechanism used to help prevent the accidental discharge of a firearm, helping to ensure safer handling....

 which use a striker-engaged firing pin

Firing pin

A firing pin or striker is part of the firing mechanism used in a firearm or explosive device e.g. an M14 landmine or bomb fuze. Firing pins may take many forms, though the types used in landmines, bombs, grenade fuzes or other single-use devices generally have a sharpened point...

, rather than the more traditional hammer

Hammer (firearm)

thumb|150px|Hammer with an integral [[firing pin]] on a [[S&W Model 13]] revolver The hammer of a firearm was given its name for both resemblance and functional similarity to the common tool...

-engaged. It uses additional precautions to prevent the firing pin from moving or being struck if the firearm were to be dropped or shaken.

The three safeties are:

• Trigger Safety: An external integrated trigger safety lever mechanism contained within the triggerguard that prevents the trigger from moving unless the lever is depressed.

• Striker Safety: A spring-loaded pin attached by an extension bar to the trigger assembly blocks the striker from striking the primer
  Percussion cap
  The percussion cap, introduced around 1830, was the crucial invention that enabled muzzleloading firearms to fire reliably in any weather.Before this development, firearms used flintlock ignition systems which produced flint-on-steel sparks to ignite a pan of priming powder and thereby fire the...
  
   of the cartridge until the trigger is pulled.

• Drop Safety: The far end of the same extension bar locks the striker into place from the rear until the trigger is pulled.

This passive safety system omits the manipulation of traditional on-off levers, hammers or external safeties as found in many other handgun designs.

However, the lack of a traditional external on-off safety means that the weapon will always fire when the trigger is depressed normally: "The ability to fire immediately, without worrying about an external safety, is one feature Glock has stressed as an advantage when selling its guns, especially to police departments...", but this has caused concern among some.

The factory standard two-stage trigger has a trigger travel of 12.5 mm (0.5 in) and the trigger pull is rated at 25 N (5.6 lbf), but by using a modified connector it can be increased to 35 N (7.9 lbf) or lowered to 20 N (4.5 lbf). In response to a request made by American

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

law enforcement agencies for a two-stage trigger with increased trigger pull, Glock introduced the NY1 (New York) trigger module, which features a flat spring in a plastic housing that replaces the trigger bar's standard coil spring. This trigger modification is available in two versions: NY1 and NY2 that are rated at 25 N (5.6 lbf) to 40 N (9 lbf) and 32 N (7.2 lbf) to 50 N (11.2 lbf) respectively, which require approximately 20 N (4.5 lbf) to 30 N (6.7 lbf) of force to disengage the safeties and another 10 N (2.2 lbf) to 20 N (4.5 lbf) in the second stage to fire a shot.