Six version options, four world generators — three of them are the same world
26.1, 26.2 and 26.x all resolve to one generator, so a seed gives identical terrain in all three. But 1.21.0 and 1.21 do not, and that catches people mid-line.
Picking a version before previewing a seed feels like it should matter every time. It does not: the seed map offers six version options and they resolve to four distinct world generators.
What each option actually selects
| option | generator |
|---|---|
| Java 1.20 | 120000 |
| Java 1.21.0 | 121100 |
| Java 1.21 | 121300 |
| Java 26.1 | 260100 |
| Java 26.2 | 260100 |
| Java 26.x | 260100 |
Three labels, one world
26.1, 26.2 and 26.x all map to 260100. World generation did not change across that line, so a seed previewed under any one of them gives byte-identical terrain, biomes and structure placement under the other two. If you are checking a seed for a 26.2 world, picking 26.1 by mistake costs you nothing.
That is the useful half of this table, because it is the case people worry about most — the current versions — and the answer is that it does not matter.
Two labels that look like one version and are not
The trap is the other end. Java 1.21.0 and Java 1.21 are different generators — 121100 against 121300. They read like the same release written two ways, and they are not: something in generation changed within the 1.21 line, and the two options exist precisely to let you pick which side of that change you want.
So the version selector matters most where the labels look most similar. A seed checked under "1.21" and played on an early 1.21 world can genuinely differ.
Why the numbers are shaped like that
The generator ids are not version strings — they are sortable integers with room between them: 120000, 121100, 121300, 260100. The gaps are deliberate. 121100 and 121300 sit two hundred apart so further 1.21-line generators can be slotted in without renumbering anything, and the jump to 260100 reflects the version-scheme change rather than any measure of how much generation moved.
The practical consequence: you cannot compare these numbers to guess how different two worlds are. 121100 → 121300 is a real terrain change; 260100 covers three whole releases with no change at all. The number tells you which generator, not how much it differs.
When the version genuinely does not matter
If you are looking up a stronghold, a village or a biome boundary for a world on any 26.x release, all three options give the same answer. Reserve the version picker for cases where you are working across a generation boundary — and those boundaries are the four rows above, not the six labels.