Category:Java Edition:Downgrade

A Downgrade Exclusive Discontinued Feature is a feature that is exclusively^[1] possible using downgrading. Downgrading is the process of updating a feature from a version of the game to a previous version, the exact opposite of upgrading. Downgrading is a dangerous and unsupported feature, risks are guaranteed and expected. Follow page instructions carefully.

All feature articles that require downgrading will have this warning:

Warning: Downgrading 

This feature uses downgrading which can result in crashes, data loss, or corruption, and requires specific versions. Follow the page instructions carefully.

Crashing and Corruption

Warning: Game Crash 

This feature can crash your game. Perform at your own risk.

Warning: Corruption 

This feature can corrupt your world. Perform at your own risk.

Downgrading has the potential risk to crash the game, cause crash loops, or corrupt world saves. This is due to the nature of downgrading. While upgrading has always been officially supported, downgrading does not have proper datafixers or safeguards in place. Depending on the downgrade, crashes and corruption may be guaranteed. Older versions are incapable of loading or processing newer content, so the game usually tries to delete anything it cannot load, but this behavior is not guaranteed. Generally, making sure incompatible things cannot be loaded is a good idea.

How to Avoid

If you want to avoid crashes or corruption, follow these general guidelines:

• Always make at least one backup of the world in case of corruption or continued crashing.
• Remove all items from your inventory that didn't exist in the version you're downgrading to. They will be deleted if loaded, but could cause crashes or an inability to load a world.
• Downgrade while in older or unimportant chunks. Newer chunks may be entirely regenerated.
• Set your render distance (and simulation distance, if applicable) to the lowest setting before loading the world to minimize the risk of the game not loading and of chunks being regenerated.
• Keep anything important far away in unloaded chunks, or even in another dimension.
• The world spawn will always load, meaning it is at an especially high risk for being regenerated. Make sure you have backups of the world's spawn region files, if you care.
• If a world still refuses to load, world save insertion or external editing may be necessary.
• Many others problems may persist. If they do, please ask for help.

Downgrades to Avoid

The level format has changed four times in Java Edition. Performing any of the following downgrades is guaranteed to corrupt your world due to incompatible formats.

• Downgrades from Infdev 20100327 (the introduction of the Alpha world format) and above to Infdev 20100325-1640 and lower will result in being unable to load the world.
• Downgrades from Beta 1.3 (the introduction of the McRegion world format) and above to Beta 1.2_02 and lower will result in being unable to load any newer chunks.
• Downgrades from 12w07a (a 1.2.1 snapshot) (the introduction of the Anvil world format) and above to 12w06a (a 1.2.1 snapshot) and lower will result in being unable to load any newer chunks. Do note that the Anvil conversion process leaves behind the old McRegion files, so you can load the last state your world had before upgrading to Beta 1.3 and above.
• Downgrades from 14w03a (a 1.8 snapshot) (the version that changed items to use namespaced IDs instead of numerical IDs) and above to 14w02c (a 1.8 snapshot) and lower will result in being unable to load any newer items.
• Downgrades from 16w32a (a 1.11 snapshot) (the version that changed entities to use namespaced IDs) and above to 1.10.2 and lower will result in being unable to load any newer entities besides players.
• Downgrades from 17w47a (a 1.13 snapshot) (the version that performed the flattening, which fundamentally changed how chunks serialized their data) and above to 17w46a (a 1.13 snapshot) and lower will result in being unable to load any newer chunks.
• Downgrades from 24w09a (a 1.20.5 snapshot) (the version that migrated item NBT to components) and above to 24w07a (a 1.20.5 snapshot) and lower will result in being unable to load any newer items, unless downgraded to 1.10.2 or before, where they will become zero stacked items.