The difficulty level of a mission in Alien Swarm can be adjusted before starting a mission. The higher the difficulty level, the tougher and more numerous the swarm will be. Friendly fire incidents will also cause more damage. On the other hand, playing on harder difficulty levels is the only way to unlock certain achievements and rewards bonus experience points.


There are five difficulty levels in total, which range from Easy—on which the Swarm suffers significant damage and speed penalties—and Brutal—on which cannon fodder are particularly resilient and can kill a healthy marine in few hits. The Swarm's endurance, speed, and damage is increased along with the difficulty level. It is not advised to play on the Insane and Brutal difficulties with only low-level weapons and equipment.

After completing a level, the game may suggest increasing the difficulty level if your squad's performance was particularly good.


Hardcore Friendly Fire ModeEdit

Hardcore Friendly Fire means that friendly fire deals full damage immediately, Flamers set teammates on fire much faster, and sentry guns will hurt you if get caught in their crossfire.

Onslaught ModeEdit

With Onslaught mode enabled, the AI Director periodically spawns waves of Drones, and randomly spawns Parasites and Shieldbugs. Onslaught mode can enabled on any difficulty level and greatly increases the number of ways a mission plays out.

Difficulty LevelsEdit

The difficulty levels and their XP ratios are:

  • Easy (50% XP)
  • Normal (100% XP)
  • Hard (120% XP)
  • Insane (140% XP)
  • Brutal (150% XP)

Speed MultipliersEdit

The speed of marines and aliens is multiplied by a factor that is correlated to the difficulty level. There is no dedicated variable for brutal difficulty, asw_alien_speed_scale_insane is changed on the fly.

Difficulty Marine multiplier Alien multiplier
Easy asw_marine_speed_scale_easy "0.96" asw_alien_speed_scale_easy "0.7"
Normal asw_marine_speed_scale_normal "1.0" asw_alien_speed_scale_normal "1.0"
Hard asw_marine_speed_scale_hard "1.024" asw_alien_speed_scale_hard "1.7"
Insane asw_marine_speed_scale_insane "1.048" asw_alien_speed_scale_insane "1.8"
Brutal asw_marine_speed_scale_insane "1.048" asw_alien_speed_scale_insane "1.9"
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