21w40a — release journal

What 21w40a changed for data packs, measured against 21w39a, the build before it. Released 2021-10-07; development build — not a release.

⚠ Entries removed

42 registry entries were removed. A pack that names one of them will fail to parse where it does.

Formats

20 entries added and 42 removed across 4 registries.

Registry	Change	Added	Removed
`block_predicate_type`	changed	`true`, `would_survive`	—
`worldgen/biome`	changed	`frozen_peaks`, `jagged_peaks`, `old_growth_birch_forest`, `old_growth_pine_taiga`, `old_growth_spruce_taiga`, `snowy_plains`, `sparse_jungle`, `stony_shore`, `windswept_forest`, `windswept_gravelly_hills`, `windswept_hills`, `windswept_savanna`, `wooded_badlands`	`badlands_plateau`, `bamboo_jungle_hills`, `birch_forest_hills`, `dark_forest_hills`, `desert_hills`, `desert_lakes`, `giant_spruce_taiga`, `giant_spruce_taiga_hills`, `giant_tree_taiga`, `giant_tree_taiga_hills`, `gravelly_mountains`, `jungle_edge`, `jungle_hills`, `lofty_peaks`, `modified_badlands_plateau`, `modified_gravelly_mountains`, `modified_jungle`, `modified_jungle_edge`, `modified_wooded_badlands_plateau`, `mountain_edge`, `mountains`, `mushroom_field_shore`, `shattered_savanna`, `shattered_savanna_plateau`, `snowcapped_peaks`, `snowy_mountains`, `snowy_taiga_hills`, `snowy_taiga_mountains`, `snowy_tundra`, `stone_shore`, `swamp_hills`, `taiga_hills`, `taiga_mountains`, `tall_birch_forest`, `tall_birch_hills`, `wooded_badlands_plateau`, `wooded_hills`, `wooded_mountains`
`worldgen/configured_feature`	changed	`monster_room_deep`, `ore_diamond_buried`, `ore_gold_lower`, `patch_berry_common`, `patch_berry_rare`	`lake_water`, `patch_berry_decorated`, `patch_berry_sparse`
`worldgen/decorator`	changed	—	`block_survives_filter`

The article has no technical-changes section — it lists bug fixes only, or predates that heading.

misode/mcmeta — 21w40a summary — formats and registries, generated from the game’s own data.
minecraft.net — 21w40a — section names only.