What is a seed ?
A seed is a random generated numbers & letters when you start a new level, you can share it with other people so they can have the same level as you.
There is also another type of seeds, these special seeds will either add a filter to the game, change the graphics, or sound effects. These special seeds won't generate the same rooms every time like a normal seed would.

Restriction
When you use a seed you can't get achievements, you can check this by looking on the left side of the screen, if there is a "gold cup" with a red sign on it, you won't be able to get achievement and maybe stats for this run.
Only a few of them won't do it.

How to enter a seed ?

1. Go in the character selection menu.
   
2. Press tab and enter a seed.
   
3. Play the game.

• BOOB TOOB - Applies a filter to the game which makes it look like an arcade machine.
  
  
  
• BL1N DEYE - Turns all enemies invisible.
  
  
  
• KAPP A - Character spawns grey, in reference to the twitch emote.
  
  
  
• DYSL EXIC - Ingame text is rearranged as though Isaac has trouble speaking.
  
  
  
• PTCH BLCK - Turns Isaac into a jet black shadow.
  
  
  
• 1TEN DSHE - Loading screen always says "Are You Sure You Want Me To Die?" But is otherwise a normal seed.
  
  
  
• CAM0 F0ES - Similar to CAM0 K1DD, but the effect is applied to the enemies as opposed to the character.
  
  
  
• 1MNO B0DY - The character is completely invisible, however you can still see the light effect surrounding him.
  
  
  
• CAMO K1DD - The player sprite is removed and replaced with a brown coloured shadow which is similar to the floor colour.
  
  
  
• FART SNDS - Sound effects are replaced with fart noises.
  
  
  
• KEEP TRAK - Removes all parts of the UI overlay, including map, consumable count, health, etc.
  
  
• BLOO OODY - leaves large circles of blood when each enemy dies, gore increased.
  Thanks to Kanvas
  
  
• HART BEAT - The lower your health is, the slower the music is.

• BASE MENT - Turns every floor into the basement.
  * This seed renders the game uncompletable. You will only be able to loop between floors one and two.
  
  
  
• BRWN SNKE - Isaac leaves a trail of poop behind him as he walks.
  
  
  
• CHAM P1ON - Turns every eligible enemy into a champion version.
  
  
  
• C0CK FGHT - All enemies have a permanent charm effect and will attack each other as if they were hostile.
  
  
  
• FEAR M1NT - All enemies have a permanent fear effect.
  
  
  
• D0NT ST0P - Player takes damage if they stop moving.
  
  
  
• KEEP AWAY - Items mimic players movement with the exception of troll bombs.
  
  
  
• SLOW 4ME2 - Everything is slow motion when Isaac stands still, but speeds up when he walks.
  
  
  
• PAC1 F1ST - Doors are left open and bosses can not be killed but they're health slowly drains like a timer.
  Thanks to Daimonas
  
  
• COME BACK - Enemies respawn once player leaves room (including bosses). New Items don't drop.
  
  
• DRAW KCAB - Inverts movement and firing controls.
  Thanks to Scaroxa
  
  
• FREE 2PAY - Starts you will 69 coins and makes it so you have to purchase all of your items and pickups.
  
  
• GULL IBLE - Starts you with 100 coins, bombs, and keys.
  
  
• THEG H0ST - Every 45 seconds, a ticking will begin, and after 5 seconds, Isaac will take 1/2 heart of damage.
  Thanks to Kanvas
  
  
• FRAI DNOT - All enemies become afraid of the player at random intervals.
  Thanks to Kanvas
  
  
• CONF ETTI - All enemies become "concussive", they move in random directions rather than their normal coded movement.
  Thanks to Kanvas
  
  
• MED1 C1NE - All pill names and descriptions show ???.
  Thanks Kanvas
  
  
• FACE D0WN - All tarot cards are face down when picked up (So they have an unknown effect).

• PEE - Unknown, but the game does accept it as a valid seed. When opening the menu the seed will be PEE C, PEE 0000, or PEE 4ME2.
  Thanks to Dubstepduck22
  
  
• ITSA SECR - Unknown, but the game does accept it. (Zelda Reference ?)
  Thanks to [FR/EN] Stalker59 and Ello_Govna
  
  
• XXXX XXZX - Unknown, Spoken by the fortune telling machine.

• HARD HARD - All mobs do 1 full heart damage or Very Hard difficulty mode ?
  Info from MrBouregard
  
  
• NRTH LION - Puts a heart in the seed section, just an easter egg ?
  
  
• P4GJ QFWH - All doors are curse doors ?

• The Binding Of Isaac: Rebirth Wikia[bindingofisaac.wikia.com]
  
• The Binding Of Isaac: Rebirth Gamepedia[bindingofisaacrebirth.gamepedia.com]
  
• More links coming soon.