F3+H turns on tooltips and lets you see the ID (even if you renamed the map) when you hover over the map but I can't find anything that tells where a filled map* is located. I'm trying to understand how this information is structured.
*item.minecraft.filled_map
I thought it might have something to do with the map number but I haven't been able to see the pattern enough to reverse engineer a location. I'm in Win 10 Java 1.16.5 with allow cheats. I have access to the file system. I figured it might be some attribute you can query but that seems to only work for mobs.
2 Answers
To find what a map actually contains, you need to first mouse over the map in your inventory, which displays the numeric ID of the map.
Once you have that ID, the next step is to read the data from the file system. The relevant file is, relative to the top-level folder the game is saved in, data/map_<#>.dat where # is the ID you found above. This is a NBT file, which has to be read using a special program (the linked question is about level.dat but map files use the same file format). The coordinates of the center of the map are then available as xCenter and zCenter tags in the data folder.
See this Minecraft Wiki article for more information on how map items are stored.
0If you want to know the exact X and Z coordinates the map marker points to, you could hold the filled map item in your mainhand, and run this command:
data get entity @s SelectedItem.tag.DecorationsThe command will output all the filled map's Decorations' (basically map markers that you see in the map) coordinates and other data in the chat.
Decorations is a list of objects that stores the data of the map markers that you see in the map, the said NBTs being x, z, rot, type, and id.
