Minecraft – Is it possible to change your single-player skin

When you say "play offline", do you mean you simply play the solo game mode? Or do you mean that you play without a net connection.

If you're playing without a connection to the internet, you won't be able to log in to your Minecraft account. Even if you've changed the skin associated with your account, when playing offline your skin will always be the default.

As of Minecraft 1.3, singleplayer and multiplayer have been merged, so you can switch your gamemode with the /gamemode command:

• /gamemode survival
• /gamemode creative
• /gamemode adventure

You can abbreviate the modes. For example, typing /gamemode c for Creative works as well.

You can only do this if you haven't disabled cheats during world generation, though.

If you turned cheats off and still want to do it for whatever reason: The game mode is stored in the level.dat file, which can be edited using an NBT editor, such as NBTExplorer. The game mode is stored in Data/GameType.