Secret Room

Secret Rooms are rooms that are not normally visible on the map and must be bombed into to access. Regular Secret Rooms are usually located next to 2 to 4 rooms, while Super Secret Rooms can only be next to one room. Very rarely, the regular Secret Room may also be located next to only one room. Entrances to Secret Rooms will never have rocks or gaps in the way. Secret Rooms usually contain at least one shopkeeper. Secret Rooms stay open after bombing them.

Variations

The following room maps were made using Basement Renovator for cleaner viewing; note that all Urns you see will be Mushrooms when encountered in-game.

Standard

ID	Weight	Contents	Image preview
0	1.0	One item.
1	1.0	Three coins.
2	1.0	Six coins.
3	1.0	Nine coins.
4	1.0	A slot machine.
5	1.0	Three random pickups and five mushrooms.
6	1.0	A chest and two TNT barrels.
7	1.0	Three pills and two mushrooms.
8	1.0	Three coins.
9	1.0	Three bomb pickups.
10	1.0	A lil' battery.
11	1.0	Two keys.
12	1.0	Two bomb pickups and four shopkeepers.
13	1.0	A key, a key master, and two mushrooms. This is the only regular secret room that doesn't have a shopkeeper.
14	1.0	A golden poop and three shopkeepers.
15	1.0	A Double bomb and twenty mushrooms.
16	1.0	A corny poop.
17	1.0	Two reward plates.
18	1.0	Four spiders and four random pickups.
19	1.0	An item behind gaps. The four rocks have equal, independent chances of being rocks, spikes, fireplaces, or iron blocks.
20	1.0	A reward plate.
21	1.0	Two rewards behind rocks and key blocks. The rewards have equal, independent chances of being a sack, item, chest, locked chest, or random pickup.
22	1.0	A nickel and three shopkeepers.
23	1.0	A sack and a restock box.
24	1.0	Ten mushrooms.
25	1.0	Two sacks.
26	1.0	Six mushrooms, two poops, and a troll bomb, which will blow up three of the mushrooms.
27	1.0	Two reward plates.
28	0.1	An item, two chests, a poop, and three black flies.
29	0.1	An item behind iron blocks, four purple fireplaces, and five shopkeepers.
30	0.1	One Mega Battery.
31	0.25	3 shopkeepers and a Rainbow Poop.
32	1	5 coins, 2 poops and 1 shopkeeper.
33	0.5	2 shopkeepers and 1 card surrounded by 4 spiked rocks.
34	0.5	One item surrounded by spikes and spiked rocks and 1 shopkeeper.
35	1	3 coins, 1 random chest surrounded by spiked rocks and 1 treasure chest, also surrounded by spiked rocks.
36	1	2 shopkeepers and 1 random chest surrounded by rocks and spikes, along with a TNT that can open up a path.
37	0.5	One Rotten Beggar and 3 coins.
38	0.5	One Wooden Chest and one shopkeeper.

Starting from the second floor of Chapter 2 onward, Greed and Super Greed have a chance to replace Secret Rooms.

Alternate Variations

Secret Rooms in alternate chapters ( Downpour, Dross, Mines, Ashpit, Mausoleum, Gehenna and Corpse) differ from the standard layouts. Each alternate floor has 11 unique layouts (12 in Downpour). Regular secret room layouts cannot appear on these floors.

Super Secret Rooms

Super Secret Rooms are only located next to one other room, and this room can't be a special room (item, shop, boss, etc.). Each Super Secret Room has set drops depending on the floor. Note that the type of Super Secret Room is not limited to certain floors it mimics (e.g. one can find a Womb-themed Super Secret Room in the Depths).

Super Secret Rooms are most likely to be found either at the end of a series of rooms that lead to a dead-end, or close to the boss room, such as the room right before the boss, if possible.

Possible Spawns

ID	Weight	Floor layout	Contents	Image preview
0	1	Womb	8 Red Hearts. Only red hearts can spawn in this room, regardless of any items. If you let Dark Bum collect the hearts, he will drop red hearts instead of soul hearts. Allow him to pick up the hearts and leave the room quickly, where he will drop the soul hearts or black hearts outside.
1	1	Cathedral	Eternal Heart. Only eternal hearts can spawn in this room, regardless of any items used. For example, using The Jar will drop Eternal Hearts on the ground instead of regular hearts. Using VI - The Lovers or V - The Hierophant will do the same, too.
2	1	Sheol	Red Chest.
3	1	Necropolis	Fortune Telling Machine.
4	1	Cellar	Random trinket.
5	1	Basement	5 pills.
6	0.5	Library	Black Heart. Only black hearts can spawn in this room, regardless of items used. This applies to VI - The Lovers, V - The Hierophant, and similar items.
7	0.1	Dark Room	Black Heart.
			4 Nulls and 5 pills or runes.
8	0.5	Burning Basement	A Shopkeeper, 2 Bomb Chests, 3 TNT, and 18 Fire Places, including Red Fire Places. All Fire Places in the room will be extinguished if this room appears in Downpour or Dross.
9	0.1	Flooded Caves	A black poop surrounded by 6 spikes.
10	0.5	I AM ERROR	Can include any of the following: Mom's Hand, Rag Man, random pickups, chests, cards, trinkets, pills, and items.
11	1	Womb	4 red poops and 3 Double Hearts.
12	0.1	Cathedral	3 Soul Hearts, 2 Blue Fire Places, and an angel Statue in the center which will drop its key piece upon death.
13	0.1	Sheol	3 Black Hearts and 2 Black Globin's Heads.
14	1	Shop	A Beggar and a Blood Donation Machine.
15	0.1	Womb	A red poop, 3 Black Flies, and a random amount of Red Hearts and Half Red Hearts. It can also contain a random amount of any other heart types, except Double Hearts.
16	0.1	Cathedral	A rainbow poop, 3 Black Flies, and 2 Eternal Hearts.
17	0.1	Sheol	A black poop, 3 Black Flies, and 6 Red Chests.
18	0.1	Shop	3 Slot Machines and 2 Fortune Telling Machines.
19	0.1	Basement	A red poop, 9 pills, and 3 Black Flies.
20	0.5	Library	One Battery Bum and 3 coins.	250px
21	0.5	Burning Basement	One Bomb Bum and 4 bombs.	250px
22	0.25	Basement	4 Greed Gapers and 1 shopkeeper.	250px
23	0.5	Corpse	3 Rotten Hearts.	250px
24	0.5	Arcade	5 Batteries#Micro-Battery micro-batteries. The middle one has a 50% chance to be a regular battery.	250px
25	0.25	Dank Depths	83% chance for a golden key and 17% chance for a golden bomb, surrounded by 4 skulls.	250px
26	0.01	Ashpit	One giga bomb that explodes shortly after.	250px
27	1	Corpse	1 Rotten Beggar and 1 Blood Donation Machine.	250px
28	0.5	Mausoleum	2 Black Sacks.	250px
29	0.25	Gehenna	One Golden Battery.	250px
30	0.25	Chest	One Mega Chest and 2 keys.	250px
31	0.5	Cellar	2 Wooden Chests.	250px
32	1	Cathedral	One Confessional.	250px

Greed Mode

In Greed Mode, Super Secret Rooms have different layouts.

ID	Weight	Floor layout	Contents	Image preview
0	1	Womb	5 Red Hearts; only Red Hearts can spawn in this room, regardless of items used.
1	1	Arcade	5 Pennies.
2	1	Caves	3 Keys.
3	1	Burning Basement	3 Bombs.
4	1	Cathedral	2 Soul Hearts. Only Soul Hearts can spawn in this room.
5	1	Library	A Black Heart. Only Black Hearts can spawn in this room.
6	1	Chest	A Chest; small chance to spawn another type of chest instead.
7	1	Chest	A Bomb Chest.
8	1	Sheol	One Red Chest. Two Red Chests.
9	1	Basement	4 pills.
10	1	Library	2 cards.
11	1	Cellar	4 Lil' Batteries. Each battery has a 50% chance to spawn as a Micro Battery instead.
12	1	Dark Room	2 runes.
13	0.5	Sheol	2 Red Chests. 3 Red Chests.
14	1	Cellar	2 trinkets.
15	0.5	Cellar	A trinket.
16	1	Bedroom	A bed.
17	1	I AM ERROR	A trapdoor to the next floor.
18	0.5	Basement	17 piles of poop.
19	0.25	The Shop	A Golden Bomb.
20	0.5	The Shop	A golden poop.
21	0.25	The Shop	A Golden Key.
22	1	Secret Room	A random item from the Greed mode Treasure Room pool.
23	1	Chest	2 Locked Chests.
24	1	Cathedral	1 Eternal Heart. Only Eternal Hearts can spawn in this room.
25	1	Womb	1 Half Red Heart. Only Half Red Hearts can spawn in this room.
26	0.1	Arcade	1 Golden Penny.	250px

Ultra Secret Rooms

Ultra Secret Rooms are special rooms that are not connected to any other rooms on the map. They can only be entered by using Red Key, Crystal Key, Cracked Key or Soul of Cain to get to a red room adjacent to it, or teleporting directly into it with XVIII - The Moon?, despite not being red rooms themselves. Ultra Secret Room doors are automatically open and do not have to be opened. If teleported into with the card, the pathway back to the rest of the level is also opened. All items generated in them will be from the Angel Room item pool.

Ultra Secret Rooms attempt to generate connected to two valid red room locations that are directly next to any non-red room on the floor. Standard methods of mapping such as Blue Map and The Mind do not reveal them, but they can be located by Cracked Orb, Book of Virtues wisps with the Book of Secrets effect, or a Rune Shard. When found, they are marked by a red ? on the map.

Most often, there will be two red rooms which are adjacent to both the Ultra Secret Room and non-red rooms. These red rooms must connect to at least one unique non-red room. This mechanic is to help figure out the possible location of the Ultra Secret Room.

Additionally, all adjacent walls of the Ultra Secret Room must connect to a valid red room location.

• In the event that no other valid location spaces, it is possible that only one red room connects the Ultra Secret Room and normal rooms.
• It is possible for the Ultra Secret Room to generate such that it requires the player to traverse through at least two red rooms.

In the Mirrored World, The Ultra Secret Room will not contain any item.

Layouts

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Notes

• Secret Rooms are found by bombing the middle of a wall in a standard size room. For larger size rooms, divide the room mentally into the size of individual rooms to figure out where to bomb. For closet-size rooms, Secret Rooms will never be found by bombing the sides but may be found by bombing the wall at the end of the closet.
• Rooms adjacent to Secret Rooms will always have a clear, walkable path to the middle of the wall where one can set a bomb. Secret Room entrances are never found in front of gaps, obstacles, or spikes. All the rooms next to a Secret Room must satisfy these requirements, so if one room near a suspicious gap in the map fails these requirements, then look elsewhere.
• If there are no valid Secret Room locations surrounded by 3 or 4 rooms, it is possible for a Secret Room to be adjacent to only 1 or 2 rooms.

A secret room adjacent to only one room

• X-Ray Vision opens all available entrances to both the Secret Room and the Super Secret Room. The I Can See Forever pill does the same for the floor on which the pill was used. Dog Tooth will play a howl sound effect if adjacent to a Secret Room or Super Secret Room, and YO LISTEN! will hover over Secret Room entrances.
• Teleportation items can randomly teleport Isaac into Secret Rooms, and XVIII - The Moon card will always teleport Isaac to the Secret Room.
• Secret Rooms are revealed on the map with Crystal Ball, Book of Secrets, XXI - The World card, XIX - The Sun card, Spelunker Hat, Blue Map, or The Mind, but you'll still need to open their entrance.
• Red Key can be used to find Secret Rooms. Lack of red door frame means a Secret Room could have generated on the other side.
• Star of Bethlehem sometimes reveals secret rooms as it can travel through them.
• If Greed or Super Greed spawn into the Secret Room, you won't be able to exit it (like a Mini-Boss room), but once the fight ends, all the exits of the Secret Room will be accessible.
• Secret Rooms can exist next to all types of rooms except Boss Rooms, allowing certain restricted rooms to be entered.
  • Even if you have no keys, it is possible to bomb into a locked special room should there exist an adjacent Secret Room. Leaving through the door will unlock the room without requiring a key.
  • It is possible to enter Curse Rooms without taking damage by bombing in from a Secret Room.
  • It is possible to access Challenge Rooms even if you don't meet the health requirements, but it is not possible to "steal" the items, as the hole will be blocked up as soon as the fighting stage begins. However, items can still be stolen by using Telepills or other teleportation items. The Challenge Room will not be accessible from the Secret Room if the Secret Room contained a fight with Super Greed. Boards will remain over the entrance to the challenge room even after the fight is over.
• Secret Rooms of all types do not exist in the Ascent.
• Once Corrupted Data is achieved (beating Delirium as Tainted Eden), items that spawn in this room have a chance to be randomized as if affected by TMTRAINER.
• Super Secret Rooms replace the dead-end room that would require the 2nd most rooms walked through from the start room to access, and cannot be connected to the secret room.
  • For reference, the Boss Room takes the dead-end room that would require the most rooms walked through, and the Shop takes the room that would require the 3rd most. This means that the Super Secret Room is equally as far or further from the start room than the Shop. It also means the Super Secret Room tends to be close to the Boss Room. Loops and large rooms connected to more than one room on any given side can tamper with this logic, however.
• Super Secret Rooms can have layouts from floors the player hasn't unlocked yet.

Trivia

• In the original The Binding of Isaac, Secret Rooms worked differently; if the player left a room after opening a Secret Room entrance, the entrance would disappear. To access the room again for any purpose, the player needed another bomb to reopen the entrance.

Seeds

PC 927Q 481S (Secret Room above Treasure Room is not attached to any others)

PC 2CC7 S7YG (Secret room is attached to only one room; located on the eastern wall in the most eastern room starting from the spawn room)

PC 419H 1DQM ( Red Key in Curse Room on your left, use it on the right of the Curse Room and the Ultra Secret Room will open up)

Bugs

Bug!	After defeating an Angel spawned in a Super Secret Room, the music will not return to the floor's regular music.

Bug!	Teleporting to the Super Secret Room in Greed or Greedier Mode, when the room is generated behind a still-locked Treasure Room, will trap the player inside.

Bug!	Sometimes Ultra Secret Room is not adjacent to four valid red rooms. (Observed on the Ultra Secret Room on the first floor of seed " L7QW 811W")