Secret Room

Secret Rooms are rooms that are not normally visible on the map and are usually accessed by bombing a wall leading to them. Regular Secret Rooms are usually located next to 3 or 4 rooms, while Super Secret Rooms can only be next to one room; they are placed on one of the dead ends generated on the map, similar to other Special Rooms. 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^[1] for cleaner viewing; note that all Urns you see will be Mushrooms when encountered in-game.

Possible Layouts

ID	Weight	Contents
0	1.0	1 Shopkeeper, 2 Fire Places, and 1 Secret Room item.
1	1.0	1 Shopkeeper, 2 Fire Places, and 3 random Coins.
2	1.0	1 Shopkeeper, 2 Fire Places, 4 Rocks and 6 random Coins.
3	1.0	1 Shopkeeper, 2 Fire Places, 4 Rocks, and 9 random Coins.
4	1.0	1 Shopkeeper, 4 Rocks, and 1 Slot Machine.
5	1.0	1 Shopkeeper, 5 Mushrooms, 4 Cobwebs, and 3 random Pickups.
6	1.0	1 Shopkeeper, 2 TNT, 4 Rocks, and 1 Chest.
7	1.0	1 Shopkeeper, 2 Mushrooms, and 3 random Pills.
8	1.0	1 Shopkeeper surrounded by 4 Cobwebs, and 3 random Coins.
9	1.0	1 Shopkeeper, 2 Fire Places, 4 Rocks in each corner, and 3 random Bomb pickups.
10	1.0 0.75	1 Shopkeeper, 2 Fire Places, 2 Red Fire Places, and a Lil' Battery.
11	1.0	1 Shopkeeper, and 2 random Key pickups.
12	1.0	4 Shopkeepers, 1 Red Fire Place, and 2 random Bomb pickups.
13	1.0	1 Key Master, 2 Mushrooms, and 1 random Key pickup. This is the only Secret Room that doesn't have a Shopkeeper.
14	1.0 0.5	3 Shopkeepers, and 1 Golden Poop.
15	1.0	1 Shopkeeper, 20 Mushrooms, and 1 Double Bomb.
16	1.0 0.25	1 Shopkeeper, 2 Fire Places, and 1 Corny Poop.
17	1.0 0.25	1 Shopkeeper, 2 Fire Places, 2 Rocks, and 2 Reward Plates.
18	1.0	1 Shopkeeper, 2 Fire Places, 20 Cobwebs, 4 Spiders, and 4 random pickups.
19	1.0 0.5	2 Shopkeepers in the upper 2 corners, with 4 more plus a Secret Room item on the other side of several gap in the floor. There are four obstacles that have equal, independent chances of being Blocks, Fire Places, Rocks, and/or Spikes; if they are Rocks, they can be bombed to bridge the gap and allow access to the room's center.
20	1.0 0.25	1 Shopkeeper, 2 Fire Places, and 1 Reward Plate.
21	1.0	1 Shopkeeper, 2 Fire Places, and several Rocks and Key Blocks blocking access to 2 rewards in the upper corners. The rewards have equal, independent chances of being Chests, Locked Chests, Grab Bags, Secret Room items, and/or random pickups.
22	1.0	3 Shopkeepers, 2 Fire Places, and 1 Nickel.
23	1.0 0.5	1 Shopkeeper, 2 Fire Places, 1 Grab Bag, and 1 Shop Restock Machine.
24	1.0 0.25	1 Shopkeeper, 2 Blocks, and 10 Mushrooms.
25	1.0 0.5	1 Shopkeeper, 2 Fire Places, and 2 Grab Bags.
26	1.0 0.5	1 Shopkeeper, 2 Fire Places, 2 Poops, 6 Mushrooms, and 1 Troll Bomb which will blow up 3 of the Mushrooms and the Shopkeeper.
27	1.0 0.25	1 Shopkeeper, 2 Fire Places, and 2 Reward Plates.
28	0.1	1 Shopkeeper, 2 Fire Places, 2 Chests, 1 Poop surrounded by 3 Flies, and 1 Secret Room item.
29	0.1	5 Shopkeepers, and 1 Secret Room item behind 4 Blocks and 4 Purple Fire Places.
30	0.1	1 Shopkeeper, 2 Fire Places, 2 Poops, and 1 Mega Battery.
31	0.25	1 Shopkeeper, 4 Fire Places, 44 Rocks, and 1 Rainbow Poop.
32	1	1 Shopkeeper, 2 Poops, 10 Mushrooms, and 5 random Coins.
33	0.5	2 Shopkeepers, 4 Fire Places, 2 Rocks, and 3 Mushrooms and 1 rock which surround 1 random Card.
34	0.5	2 Shopkeepers, 2 Fire Places, 1 Spiked Rock in each corner, and 1 Secret Room item behind Blocks, Key Blocks, and Spikes.
35	1	1 Shopkeeper, 3 random Coins, along with 1 Chest and 1 Locked Chest each in the upper corners that are both blocked by 2 Spiked Rocks.
36	1	2 Shopkeepers, 1 Spiked Rock in each corner, and 1 random Chest that is surrounded by Rocks, which can be destroyed with 1 nearby TNT which is itself behind Spikes on each side.
37	0.5	One Rotten Beggar, 4 Mushrooms, and 3 random Coins.
38	0.5	1 Shopkeeper, 2 Fire Places, 1 Block in each corner, and 1 Wooden Chest.

Starting from the first floor of Chapter 3 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; in other words, it is placed on one of the floor's dead ends, like any other Special Room. 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. Isaac can find a Womb-themed Super Secret Room in 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, and are particularly likely to appear near the Boss Room, as they are the second room type to be placed on a map during Map Generation, and are therefore placed far away from the room Isaac starts in. Because Shops are the third type of room generated, super secret rooms are also likely to spawn near the shop, and are likely to spawn in between the shop and the Boss Room.

Possible Layouts

ID	Weight	Room theme	Contents
0	1	Womb	8 random Red Hearts. Only Red Hearts can be created in this room, regardless of what item is used to create said Hearts (e.g. V - The Hierophant will create 2 Red Hearts rather than Soul Hearts).
1	1	Cathedral	1 Eternal Heart. Only Eternal Hearts can be created in this room, regardless of what item is used to create said Hearts (e.g. V - The Hierophant will drop 2 Eternal Hearts rather than Soul Hearts).
2	1	Sheol	1 Red Chest.
3	1	Necropolis	1 Fortune Telling Machine.
4	1	Cellar	1 random trinket.
5	1	Basement	5 random Pills.
6	1	Dark Room	1 Black Heart. Only Black Hearts can be created in this room, regardless of what item is used to create said Hearts (e.g. V - The Hierophant will drop 2 Black Hearts rather than Soul Hearts).
6	0.5	Library
7	1 0.25 0.1	Dark Room	1 Nulls in each corner, and 5 random Runes.
8	1 0.5	Burning Basement	1 Shopkeeper, 2 Bomb Chests, 3 TNT, 13 Fire Places, and 5 Red Fire Places. All Fire Places in the room will be extinguished if this room appears in Downpour or Dross.
9	1 0.1	Flooded Caves	1 Black Poop surrounded by 6 retracting Spikes.
10	1 0.25 0.5	I AM ERROR room	Can contain any of the following: Mom's Hand, Rag Man, random pickups, Chests, Cards, trinkets, Pills, and/or 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 which will summon an Angel if blown up, who will then drop a Key Piece upon death. Only Soul Hearts can be created in this room, regardless of what item is used to create said Hearts (e.g. The Lovers will drop 2 Soul Hearts rather than Red Hearts).
13	0.1	Sheol	3 Black Hearts, and 2 Black Globin's Heads. Only Black Hearts can be created in this room, regardless of what item is used to create said Hearts (e.g. V - The Hierophant will drop 2 Black Hearts rather than Soul Hearts).
14	1	Shop	1 Beggar, and 1 Blood Donation Machine.
15	0.1	Womb	1 Red Poop surrounded by 3 Flies, and a random number of various types Red Hearts, except Double Hearts.
15	0.1	Scarred Womb
16	0.1	Cathedral	1 Rainbow Poop surrounded by 3 Flies, and 2 Eternal Hearts. Only Eternal Hearts can be created in this room, regardless of what item is used to create said Hearts (e.g. V - The Hierophant will drop 2 Eternal Hearts rather than Soul Hearts).
17	0.1	Sheol	1 Black Poop surrounded by 3 Flies, and 6 Red Chests.
18	0.1	Shop	2 Fortune Telling Machines and 3 Slot Machines.
19	0.1	Basement	1 Red Poop surrounded by 3 Flies, and 9 random Pills.
20	0.5	Library	1 Battery Bum, 4 Urns, 2 Cobwebs, and 3 random Coins.
21	0.5	Burning Basement	1 Bomb Bum, 3 Rocks and 3 Fire Places in each corner, and 4 random Bomb pickups.
22	0.25	Basement	1 Shopkeeper, and 4 Greed Gapers.
23	0.5	Corpse	1 Spiked Rock in each corner, and 3 Rotten Hearts. Only Rotten Hearts can be created in this room, regardless of what item is used to create said Hearts (e.g. V - The Hierophant will drop 2 Rotten Hearts rather than Soul Hearts).
24	0.5	Arcade	5 Micro Batteries. The middle one has a 50% chance to be a Lil' Battery.
25	0.25	Dank Depths	1 pickup which has an 83% chance to be a Golden Key and a 17% chance to be a Golden Bomb, surrounded diagonally by 4 Skulls.
26	0.01	Ashpit	8 Mushrooms, and 1 lit Giga Bomb that explodes shortly after.
27	1	Corpse	1 Rotten Beggar, and 1 Blood Donation Machine.
28	0.5	Mausoleum	3 Urns in each corner, and 2 Black Sacks.
29	0.25	Gehenna	4 Spikes, and 1 Golden Battery.
30	0.25	Chest	1 Mega Chest, and 2 random Key pickups.
31	0.5	Cellar	4 Rocks, and 2 Wooden Chests.
32	1	Cathedral	1 Confessional.

Greed Mode Layouts

Greed Mode has its own set of Super Secret Room layouts.

ID	Weight	Room theme	Contents
0	1	Womb	5 Red Hearts. Only Red Hearts can be created in this room, regardless of what item is used to create said Hearts (e.g. V - The Hierophant will create 2 Red Hearts rather than Soul Hearts).
1	1	Arcade	5 Pennies. One of which can be any type of Coin.
2	1	Catacombs	3 Keys.
3	1	Burning Basement	3 Bombs.
4	1	Cathedral	2 Soul Hearts. Only Soul Hearts can be created in this room, regardless of what item is used to create said Hearts (e.g. VI - The Lovers will create 2 Soul Hearts rather than Red Hearts).
5	1	Library	1 Black Heart. Only Black Hearts can be created in this room, regardless of what item is used to create said Hearts (e.g. V - The Hierophant will create 2 Black Hearts rather than Soul Hearts).
6	1	Chest	1 Chest; small chance to spawn another type of Chest instead.
7	1	Chest	1 Bomb Chest.
8	1	Sheol	1 Red Chest.
8	1	Sheol	2 Red Chests.
9	1	Basement	4 random Pills.
10	1	Library	2 random Cards.
11	1	Cellar	4 Lil' Batteries. Each battery has a 50% chance to be a Random Battery instead.
12	1	Dark Room	2 random Runes.
13	1	Sheol	2 Red Chests.
13	0.5	Sheol	3 Red Chests.
14	1	Cellar	2 random trinkets.
15	1.0 0.5	Cellar	1 random trinket.
16	1	Clean Bedroom	1 bed.
17	1	I AM ERROR room	1 trapdoor to the next floor.
18	1 0.5	Basement	17 Poops.
19	1 0.25	The Shop	1 Golden Bomb.
20	1	The Shop	1 Golden Poop.
21	1 0.25	The Shop	1 Golden Key.
22	1	Secret Room	1 Greed Mode Treasure Room item. 1 Greed Mode Secret Room item.
23	1	Chest	2 Locked Chests.
24	1	Cathedral	1 Eternal Heart. Only Eternal Hearts can be created in this room, regardless of what item is used to create said Hearts (e.g. V - The Hierophant will create 2 Eternal Hearts rather than Soul Hearts).
25	1 0.1	Womb	1 Half Red Heart. Only Half Red Hearts can be created in this room, regardless of what item is used to create said Hearts (e.g. V - The Hierophant will create 2 Half Red Hearts rather than Soul Hearts).
26	0.1	Arcade	1 Golden Penny.
27	0.5	Necropolis	1 Greed Mode Secret Room item surrounded by pits and 2 spike rocks that can fill up pits when destroyed from a certain direction.

Ultra Secret Rooms

Ultra Secret Rooms are special rooms that are not connected to any other room on the map directly. They are not revealed by most mapping effects (The Mind, etc.) and can only be revealed on the map with Cracked Orb, Book of Secrets, wisps, and Rune Shard. They can be accessed directly by opening Red Rooms adjacent to them using Red Key or Red Key wisps, Crystal Key, Cracked Key, and Soul of Cain: entering a Red Room next to the Ultra Secret room will reveal its position and automatically open the doorway leading into it. It can also be entered by teleporting to it using XVIII - The Moon?; when teleported into, a pathway of Red Rooms back to the rest of the level will be opened automatically. Ultra Secret rooms contain items from the Ultra Secret Room item pool.

Common Ultra Secret Room locations

Ultra Secret rooms are most likely generated in spots that connect to 3+ non-red rooms through its adjacent red rooms (different squares in L rooms count as 2). They can be connected to 2 or 1 non-red rooms through its adjacent red rooms, but a specific 3+ room location is 11.5x more likely than a specific 2 room location, and 1 room locations being virtually impossible if there is a 3+ location available. If there is no 3+ room location available then a specific 2 room location is 11.5x more likely than a specific 1 room location.

Ultra Secret Rooms can't be connected to red rooms that connect to Secret Rooms, Super Secret Rooms, or Curse Rooms, and can't be in a location where any of its adjacent red rooms are invalid, such as next to a Boss Room (Boss Rooms in The Void can have red rooms next to them, but the Ultra Secret Room will never be connected to one), next to the sides of narrow rooms, or any room that can't have a red room opened on that specific side, however locations on the 13x13 border where a red room would normally open to an I AM ERROR room are allowed.

Notes

Generally, the best strategy for finding Ultra Secret Rooms is by checking a location that connects to at least 3 non-red rooms through its adjacent red rooms (in which all sides can have red rooms created, and isn't next to a Secret, Super Secret, or Curse Room), and if it's not in any 3+ locations, checking the spots connected to 2 rooms, then 1.
- When choosing which side to open from, the best way to increase your odds is to open the red room that connects to the highest number of other potential Ultra Secret Room locations.
  - However, there is also value in choosing to open a red room that connects to an otherwise hard-to-access room, such as a Boss Challenge Room.
- If the only remaining valid locations are connected to a single non-red room, it's just as likely for the Ultra Secret Room to be connected to the side of a single room as it is connected to a corner.
The doors of the Ultra Secret Room are opened automatically only when approached from the outside. If other rooms exist adjacent to it, the doors will not open from inside the Ultra Secret Room without bombing them or returning from the outside.
- Red Key or Cracked Keys must be used before the bombs, as otherwise explosions won't have an effect.
The Ultra Secret Room can generate north of the Mega Satan door, despite not being able to create a red room there.
In the Mirrored World, the Ultra Secret Room will be empty, same as any Special Room.
It's possible for the Ultra Secret Room to not generate if there are no valid locations.

Layouts

ID	Weight	Contents
0	1.0	2 Shopkeepers, 4 Poops behind Key Blocks, some Cobwebs, 2 random Keys, and 1 Ultra Secret Room item.
1	1.0	Several Key Blocks and Metal Blocks along the walls, and 1 Ultra Secret Room item.
2	1.0	2 Shopkeepers, several Key Blocks, and 1 Ultra Secret Room item.
3	1.0	1 Shopkeeper behind Key Blocks, a few Cobwebs, and 1 Ultra Secret Room item blocked off by Key Blocks and Metal Blocks.
4	0.75	1 Shopkeeper, a few Cobwebs, and Rocks in the shape of a Key, with 1 Ultra Secret Room item inside the Key's 'loop'.
5	0.5	2 Shopkeepers, a few Cobwebs, several Urns, 3 random Coins, and 4 Greed Gapers guarding 1 Ultra Secret Room item.
6	0.25	10 Shopkeepers, 2 Fire Places, a Rock, some Cobwebs, and 2 Ultra Secret Room items.
7	0.1	2 Shopkeepers, some Cobwebs, a Rock, 10 Keys, and 2 Key Rings.
8	1.0	1 Shopkeeper, some Cobwebs, 1 Key Block in each corner, and an item between some Retractable Spikes.

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.
One easy strategy to place the bomb correctly in large rooms is to position Isaac in a corner, walk along a wall, then place the bomb at the spot where the camera starts moving.
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 Isaac can place a bomb. Secret Room entrances are never found in front of gaps, obstacles, spikes, or places that enemies spawned when the room was originally entered. Each room adjacent 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.
Secret Rooms are equally as likely to be in a valid location with 3 neighbors, as it is with 4 neighbors. 2 neighbor locations are rare but possible, even when there are locations with 3+ neighbors available. 1 neighbor locations can only happen if there are no valid 3+ neighbor locations, and are very rare.

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 when Isaac enters a room 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 will always teleport Isaac to the Secret Room.
Secret Rooms are revealed on the map with Blue Map, Book of Secrets, Crystal Ball, The Mind, Spelunker Hat, XIX - The Sun, or XXI - The World, but Isaac will still need to open their entrance.
Red Key can be used to find Secret Rooms. The 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 inside a Secret Room, Isaac 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.
- An exception to this is that Challenge Rooms and Boss Challenge Rooms will be inaccessible; the metal bars won't be removed from walls that lead to them after the fight concludes.
Secret Rooms can exist next to all types of rooms except Boss Rooms, Super Secret Rooms, and other Secret Rooms; allowing certain restricted rooms to be entered.
- Even if Isaac has 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 Isaac doesn'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.
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 Secret Rooms have a chance to be "glitched" 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.
- Sometimes, the Boss Room will not be the furthest dead-end room; usually, in these cases, the Boss Room has one side blocked off and the Super Secret Room will be connected to the furthest normal room, with the wall leading to it being on the opposite side of the blocked off side in the Boss Room.
  - For example, if the blocked off side in the Boss Room is to the north, the Super Secret Room will be to the south of the furthest normal room.
Super Secret Rooms can have layouts with themes from floors that Isaac 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.
- For some reason, Challenge Rooms and Boss Challenge Rooms still work this way.
Prior to V1.7.5, Ultra Secret Rooms used the Angel Room Item Pool. This was meant as a placeholder.

Bugs

Bug!	After fighting Greed/Super Greed spawn inside a Secret Room, if there is an adjacent Challenge Room or Boss Challenge Room, the metal bars from the Greed/Super Greed fight will not disappear after the fight has ended, making it impossible to enter the Challenge/Boss Challenge room this way.

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