21w41a — release journal

What 21w41a changed for data packs, measured against 21w40a, the build before it. Released 2021-10-13; development build — not a release.

⚠ Breaking for data packs

This build removed 2 registries. Any file that referenced them stops loading.

Formats

14 entries added and 52 removed across 5 registries.

Registry	Change	Added	Removed
`worldgen/configured_surface_builder`	registry removed	—	`badlands`, `basalt_deltas`, `crimson_forest`, `desert`, `end`, `eroded_badlands`, `frozen_ocean`, `full_sand`, `giant_tree_taiga`, `grass`, `gravelly_mountain`, `grove`, `ice_spikes`, `lofty_peaks`, `mountain`, `mycelium`, `nether`, `nope`, `ocean_sand`, `shattered_savanna`, `snowcapped_peaks`, `snowy_slopes`, `soul_sand_valley`, `stone`, `stone_shore`, `stony_peaks`, `swamp`, `warped_forest`, `wooded_badlands`
`worldgen/surface_builder`	registry removed	—	`badlands`, `basalt_deltas`, `default`, `eroded_badlands`, `frozen_ocean`, `giant_tree_taiga`, `gravelly_mountain`, `grove`, `lofty_peaks`, `mountain`, `nether`, `nether_forest`, `nope`, `shattered_savanna`, `snowcapped_peaks`, `snowy_slopes`, `soul_sand_valley`, `stone_shore`, `stony_peaks`, `swamp`, `wooded_badlands`
`worldgen/material_condition`	new registry	`biome`, `hole`, `noise_threshold`, `not`, `steep`, `stone_depth`, `temperature`, `water`, `y_above`	—
`worldgen/material_rule`	new registry	`bandlands`, `block`, `condition`, `sequence`	—
`worldgen/configured_feature`	changed	`dark_forest_vegetation`	`dark_forest_vegetation_brown`, `dark_forest_vegetation_red`

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

misode/mcmeta — 21w41a summary — formats and registries, generated from the game’s own data.
minecraft.net — 21w41a — section names only.