Java vs Bedrock: Structure Placement

What the two editions share

Minecraft 1.18 rebuilt Overworld terrain and biomes around a set of noise functions, and Bedrock adopted the same functions with the same 64-bit seed. From that version on, the biome at any X and Z is the same on both editions for the same seed. The map takes advantage of this: it runs one biome generator and only switches the structure algorithm when you change the edition.

Spawn is shared as well, at least approximately. Seed 0 spawns at -32, 0 in a forest on both editions, and seed 6942069420694206 spawns at 0, 0 in a sparse jungle on both. Text seeds hash identically too, because Bedrock copied Java's String.hashCode for them.

That is where the sharing ends. Everything that is placed on top of the biome map, from villages to slime chunks, is decided by random numbers, and the two editions draw their random numbers from different generators.

How Java places a structure

Java divides the world into square regions of chunks, with a size and a minimum gap per structure type: villages use 34-chunk regions with an 8-chunk separation, trial chambers 34 and 12, ancient cities 24 and 8, woodland mansions 80 and 20. In each region it seeds java.util.Random with the world seed, the region coordinates and a salt unique to the structure type, draws one chunk position inside the allowed part of the region, and then checks the biome there. If the biome fits, the structure generates at that chunk; if not, the region stays empty.

Because the draw only depends on the seed, the region and the salt, a seed map can compute every attempt for the whole world without generating any terrain. The biome check is the slow part, and it is the part that decides which attempts become real structures.

How Bedrock places a structure

Bedrock uses the same idea of regions, often with the same sizes, but a different generator. It builds a 32-bit region seed from the region coordinates, the structure's salt and the low 32 bits of the world seed, then feeds it to a Mersenne Twister. Some types take one draw per axis; others take two and average them, which pulls positions toward the middle of the region. Bedrock also offsets the final block position by 8 inside the chunk.

Different generator, different numbers, different chunk. That alone is why a Java village finder gives wrong answers for Bedrock: the village attempt lands in a different chunk of the same region. The map implements the Bedrock algorithm for each type where it is known, and it was checked against the Bedrock Dedicated Server by asking the game whether a structure exists at each marker.

On seed 0, the nearest village to spawn is a savanna village at 608, 720 on Java and a savanna village at 232, 696 on Bedrock. Both are savanna villages because both editions see the same biome map; they are in different places because the dice are different.

Strongholds, slime chunks and the other dimensions

Java places exactly 128 strongholds in rings around the origin, three of them between 1,280 and 2,816 blocks out. Bedrock has no rings. It generates strongholds under some villages and scatters more far away, so the nearest Bedrock stronghold is often several thousand blocks out: on seed 0 the first one the map lists is at -3528, 1896, almost 4,000 blocks from spawn. The map shows the village-linked strongholds for Bedrock; the scattered ones are not shown because their placement could not be confirmed in-game.

Slime chunks are the most extreme case. Java mixes the world seed with the chunk coordinates, so the pattern is unique to the seed. Bedrock seeds its generator with the chunk coordinates alone, so every Bedrock world has the same slime chunks. A Bedrock slime chunk list works in every Bedrock world and in no Java world.

The Nether and the End do not share generation either. Bedrock's Nether biomes differ from Java's, so the map hides the Bedrock Nether biome layer instead of drawing Java's, while fortresses and bastions use Bedrock's own placement and are confirmed in-game. The Bedrock End is laid out differently from Java's, and End cities are marked Java only because an End city attempt from the Java rules is usually not there on Bedrock.

What the map guarantees for Bedrock

Every structure type carries a Bedrock status in the engine, measured by asking the Bedrock Dedicated Server whether the structure exists at the map's marker. Three groups come out of that.

The approximate group admits something many tools hide: on Bedrock, roughly half of the mansion and shipwreck attempts do not generate, because the game's own checks fail after placement. The map still shows them, with an approximate badge, because the ones that do exist are at those coordinates.

Choosing the right edition and version

Set the edition to the game you play, then pick the version band. Bedrock version numbers do not match Java's, so the map lists the Bedrock ranges that use each generator.

Bedrock versions before 1.18 are not supported at all, because their Overworld generator was different from Java's and is not part of the engine. If you play on a console or phone, you are on Bedrock; the Java edition is the desktop version with the launcher.