From DoomWiki.org

Jumping is meant here as adding an upwards impulse to the avatar by a user activity.

This can be achieved for a number of source ports which implement jumping by using an input device key which can be bound to a dedicated jumping feature.

Jumping was not implemented originally in the Doom engine, and neither Doom nor Heretic offer it; however, it was added to both Hexen and Strife.

When jumping is not possible, the maximum elevation that the player can step up is 24 map units (16 in Strife), allowing creation of "ridiculously low walls" that must be lowered or otherwise worked around before the player can reach what lies in plain sight behind, for example a power-up, key, or switch. When using a source port that allows jumping in Doom or Heretic, it can be considered a cheat with potential to break the normal flow of maps not designed with jumping in mind. Because of this, some source ports allow disabling jumping on a per-map basis with a keyword in MAPINFO. Doom 64 EX allows access to a jumping feature not found in the original Doom 64 after completing the secret level (Hectic) using the three-key exit, via the "Features" menu where other cheats are found.

More limited methods of jumping include:

  • The player avatar, in contrast to most non-flying monsters, is able to step up even narrow stairs. This has been used in designing pseudo-ladders to implement a climbing-like behavior for games which do not support special climbable walls. Running up stairs allows the player avatar to continue its movement in a ballistic curve beyond the top of the stairway, in a certain range (this effect is rather limited).
  • In source ports where looking up and down is allowed by the engine, firing an explosive at the ground and running over it often causes the player to be lifted by the blast radius to allow so-called rocket jumping. Some fan-made deathmatch maps are designed with areas only accessible via rocket jumping. This is not possible in the original engine, however; firing an explosive to the player's feet in Heretic (with the Phoenix Rod) or Strife (with the Mini-missile launcher) will only cause horizontal recoil.
  • Another risky way due to the received damage: Getting "successfully" attacked by an arch-vile also raises the player avatar briefly; this is referred to as arch-vile jump.