Coopedit

This mode is used for editing maps online, with more than one person. For example, some clans do this with their members.

By default coopedit is restricted as a vote on servers. However, if you are playing on a server where it is enabled, the vote can be initiated by typing this command:

/coop mapname

You can also use this mode without connecting to a server. Of course, you can press 'E' in every singleplayer mode, but co-op edit mode has the advantage of not having a time limit.

Restrictions
When co-op editing is done on a server (in multiplayer mode), there are a few restrictions which stop the player from using a few commands. You cannot use the copy and paste command, which is useful in single player mode, you can also not use the undo button in edit mode so when you do something you have to change it back manually. You cannot place slopes or arches using the menu or commands, you have to do it manually with heightfields.

You can use all editing commands in singleplayer co-op edit mode.