A flash hider is a device that is attached to the muzzle of a firearm to help reduce the visible signs of the burning gases that escape from the muzzle when a round is fired. Flash hiders work by intercepting some of the gas and directing it forward and away from the shooter, helping to reduce both the glare and noise of the gunshot. There are many different designs of flash hiders, but they all serve essentially the same purpose.
In general, flash hiders are more commonly found on larger caliber weapons where muzzle blast is more pronounced. However, they can be used on any type of firearm to help reduce its signature. In some cases, a flash hider may also be paired with a muzzle brake to further reduce recoil.
Matthew Edited answer July 1, 2022