Java Edition 1.15.1 Pre-release 1

1.15.1 Pre-release 1 (known as 1.15.1-pre1 in the launcher) is the first pre-release for Java Edition 1.15.1, released on December 12, 2019.

Changes

 * Optimized chunk rendering performance, especially for chunks with many different block states
 * Fixed an error spammed to the game's log files caused by custom spawner blocks spawning villagers
 * Improved network handling of invalid biome ids
 * Fixed a crash in the Realms screen