Tutorials/Downgrading

Downgrading is the act of loading a world in an older version than the version of that world last loaded. Downgrading is dangerous; it causes the world to be prone to corruption, data loss or crash.

Downgrading screen
In the singleplayer menu, if a world was last loaded in a version newer than the one being run, the version name of the world is displayed in red. When moving the mouse over the world, an exclamation mark appears to the left of the play button in the world icon on the left. While hovering over the world icon, the exclamation mark turns red and a tooltip appears with red text stating: "World was saved in a newer version, loading this world could cause problems!". Trying to load the world causes a screen to pop up with text that says: "Downgrading a world is not supported This world was last played in version ; you are on version . Downgrading a world could cause corruption — we cannot guarantee that it will load or work. If you still want to continue, please make a backup!" The screen also has three buttons: "Create Backup and Load", "I know what I'm doing!", and "Cancel". The actions when clicking are shown in the table below.

When downgrading a world, the version of the world when it was last loaded will change to the current version.

Benefits

 * Being able to obtain an infinite supply of enchanted golden apples, since you could craft them before 1.9
 * Obtaining "god armor", a maxed out armor set which has all types of Protection, which was only obtainable from 1.14 to 1.14.2
 * Execute duplication glitches that are patched in latest versions but are still working in older versions

Consequences
The consequences of downgrading a world are of follows:
 * Any loaded chunks in the world update to the new chunks.
 * Any blocks, items, entities, enchantments, effects, particles, sounds, biomes, banner patterns and advancements that don't exist in that version are removed from the world.
 * Downgrading a world can cause the world to corrupt, lose data, and possibly crash.
 * Makes selected chunks in the world have strange rigid borders.
 * Some buildings/structures you made can be erased from existence, note that some will convert to their older version, such as villages.
 * Biomes can change, commonly when a biome existed in one version, but not the other, such as the mangrove swamp.
 * Even upgrading back to the version the world was originally created in will not give everything that was lost back, such as enchantments.
 * Floating things that shouldn't float such as vines, can appear, such as when a mangrove swamp is brought to 1.18.

Steps to downgrade your world
For example, if you're on version 1.19 and want to get infinite enchanted golden apples, don't directly downgrade the world to version 1.8. Instead, set your render distance to the lowest, go around 200 blocks away from spawn and then downgrade your world to a version after 1.8 but before the latest version (for example, 1.13-1.15). This is required so that the world shows up on the 1.8 world selection menu. Then go to version 1.8 and craft your enchanted golden apples.

Before doing this though, put your items in an unloaded chunk so that they'll be safe and won't get deleted by the game. Also, try to avoid places that have newer blocks/items/structures/biomes, etc., as the game will get confused and will immediately delete the newer additions, as they didn't exist yet in those versions.