Minecraft will generate quite a few files in your world folder when you create a world. Most of these files are not needed and by deleting them you can reduce the file size when it comes to uploading your world.
Below is a table which displays all the files that may be generated in your world folder, along with a description and whether or not the file is required.
|YES||Stores global information about the world such as name and generation type.|
|YES||Contains all the region files of your world.|
Individual region files using extension should not be included if the world was converted to Anvil.
|DEPENDS||Stores map data for craftable maps — remove if you are not using custom map items|
|NO||A backup of level.dat before the map was converted from the MCRegion world format to Anvil. This is typically seen in older maps built before Minecraft 1.2.1.|
|NO||A backup of an older version of the level.dat file.|
|NO||A timestamp when the level was last accessed. This is typically seen while a map is actively being used or modified by a third-party program.|
|or||NO||Contains files which store the individual states of each player.|
|NO||Stores information about Villages in the world.|
|NO||Contains all the region files for The Nether () and The End ().|
|NO||Contains achievements and other statistics.|
|NO||Generated while a map is being edited in MCEdit.|
|NO||Typically seen in maps that was loaded on Minecraft with mods involving chunk loaders.|
|NO||Generated by MCEdit or NBTEdit.|
|NO||Generated by Not Enough Items.|
|NO||Generated by Single Player Commands.|