Simply type the code while in-game, and the code should work. The screen should flash and in most cases a purple message will appear on top, indicating that the cheat code worked.

AEOMG - God mode. Makes the player invulnerable to all damage and insta-kills, including damage/death cheats. Shows health as ∞. Does not actually change health itself, so the player can still activate health pickups. - "God mode enabled" - "God mode disabled"
AEOMEGA - God mode (like AEOMG) + Infinite mana! - "Woundless with weapons!" - "Back to normal."
AEMAGE - Gives full mana. - "Full mana"
AEWIZARD - Gives all weapons + mana + keys. - "You're a wizard, Larry."
AENIMA - Soul mode engage. Fills soul meter to the maximum. - "Soul power!"
AEBABY - Soul mode toggle. Permanently activates soul mode, regardless of the amount of souls. Does not work if soul power is active. - "Perma-soul activated" - "Perma-soul deactivated"
AEWARLOCK - Gives all weapons, but not mana. - "All weapons given"
AEWEP(2-7) - Gives a certain weapon depending on the number.
AELEON - Level select screen. Shows levels depending on the chosen game version (base game or DLC).
AE1981 - CGA palette 1. - "CGA mode 1"
AE1982 - CGA palette 2. - "CGA mode 2"
AE1983 - CGA palette 3. - "CGA mode 3"
AE1989 - EGA palette. - "EGA mode"
AE1990 - VGA palette. - "256 colour mode"
AE2000 - Full colour palette. - "Full colour mode"
AEURP - Burp. - "Excuse me..."
AEBORT - Quits the game.
AENDREW - Music select screen. Allows player to play only one of the level track's variations. Make sure to press "Ok" after choosing the track because if you open the main menu while music select menu is on it will freeze on the screen and this can only be resolved by restarting the level. - "Music select"
AERO - Fly mode. Permanently activates flight. Deactivates when the player enters water. - "I believe I can fly..." - "Oh ♥♥♥♥... I was trippin'"
AESEE - Torch mode. Activates the torch powerup. - "Torchlight"
AEYESORE - Invisibility powerup. Permanently makes player invisible. - "Now you don't"
"Now you see me"
AELPHA - Gives all powerups + keys + weapons + mana + health + fullfils soul meter. - "Fully tourqed"
AEVAIN - Gives all keys. - "All keys given..."
AEHEH - Finishes level. Does not set an episode as finished when used on the final level. - "Ok then..."
AETHER - Noclip mode. Allows the player to fly through everything. Does not make the player immune to AEOUCH or AESPLODE cheats. If the player types AERO while this cheat is active, flight is going to be deactivated but the player will fall through the floor into the abyss (not this one). If the player activates a flight powerup and then uses this cheat, they will get stuck in the air after the powerup runs out. - "No clipping enabled." - "No clipping disabled."
AESTHETIC - Vaporwave mode. Changes colour palette and music. Ignores the music track variable visible in AESTAT. - "+ Aesthetic Mode +" - "Snap back to reality"
AETHEORY - Turn all post processing up to max. Can only be deactivated by typing other palette cheats (AE1989, AE2000, AESTHETIC and etc). - "My eyes!!!!!!"
AELYMPICS - Makes the player walk super fast. - "Gotta go fast!!!" - "*Skidding noise"
AEON - Makes the game slow. - "Slowpoke Rodriguez" - "Back to normal"
AEXTREME - Super fast weapons. Every player's weapon swings/shoots significantly faster. - "Superfast weapons enabled." - "Superfast weapons disabled."
AEXTINCT - Kills all enemies on a level and prevents them from spawning. Does not add removed enemies to the kill counter. - "Wipe them out... All of them..."
AESPLODE - Kills the player. - "Goodbye cruel world :("
AEOUCH - Hurts the player. Deals 1 point of damage unless AEOMG / Invulnerability powerup is active. - "Ow."
AESTOP - Freezes enemies. Does not affect unspawned enemies. - "Freezin' enemies" - "Thawin' enemies"
AEHIDE - Hides weapons (except for planets).
AESHOT - Hides messages + HUD (screenshot mode)

Using any of these cheats grants the achievement "Filthy Cheater"