1.21.9 Release Candidate 1 — release journal
What 1.21.9-rc1 changed for data packs, measured against 1.21.9-pre4, the build before it. Released 2025-09-25; development build — not a release.
💡 No measured change
Same data pack format, same registries. That is the strongest safe-for-data-packs signal a diff can give, and it is still not proof — behaviour changes and bug fixes are invisible to it.
Formats
| 1.21.9-pre4 | 1.21.9-rc1 | |
|---|---|---|
| Data pack format | 88.0 | 88.0 |
| Resource pack format | 69.0 | 69.0 |
| Data version | 4552 | 4553 |
Registries
No registry gained, lost or changed an entry.
The official notes
Read the 1.21.9 Release Candidate 1 article on minecraft.net.
The article has no technical-changes section — it lists bug fixes only, or predates that heading.
Minecraft Wiki page for 1.21.9-rc1.
In the journal
← 1.21.9-pre4 · All builds · 1.21.9 →
Sources
- misode/mcmeta — 1.21.9-rc1 summary — formats and registries, generated from the game’s own data.
- minecraft.net — 1.21.9 Release Candidate 1 — section names only.