Codes are Entered in the Options Screen which is located in the upper right part of the screen just under the FPS Counter.

Daily code - This will show up as an image in the codes screen ingame that you can click to type it for yourself and then click redeem.
"protto" : Rewards: 500 Antimatter & 2 random Potions

"AWholeNewUniverse" : 10.000 Antimatter - Requires Normal Difficulty unlocked
"IntoTheSingularity" : 7.500 Antimatter - Requires 1 Black Hole Travel
"MechILikeToFind" : 1 Mech Token - Requires 1 Black Hole Travel, Reusable after Super Nova.
"GICOnSteam": 7.500 Antimatter to celebrate Steam launch
"SirMoarAntimatterNow": 500 Antimatter & 3x (Hp, Dmg, Junk, Plasma, Exp) Potions
"AndLeftSomeGoodies": 1000 Antimatter & 3x (Prisoners, Citizens) Potions - Reach Galaxy #2 Solar System #3
"PotatoLover": 5000 Antimatter - Reach Boss Stage in Planet #5 Required
"TyForHelp": 1000 Antimatter
"PeekABooFoundYou" : 500 Antimatter - Hidden Code, you need to find it to unlock its benefits!
Hints to help find it:
"You need to click something small on the main screen"
"It's on the Main screen, with no other UI/menus open"
"What you need to click is on the right hand side of the screen"

Added [10/17/2024]
"FindYourDaringAntimatter": 2.500 Antimatter & 5x (Meteorite, Minerals, Radiations) Potions - Requires SuperNova #1

Added [12/24/2024]
"XtraMiniAntimatterSupply": 3.000 Antimatter & 5x (Hp, Damage, Junk, Plasma, Exp) Active Potions - Planet #2 Completed required