Copy and paste works in most text fields in Minecraft using the normal keyboard shortcuts, but there are a few places it behaves differently from other programs.
The basics
Control and C copies, Control and V pastes, Control and A selects everything in the field. On a Mac, use Command instead. This works in the chat box, on signs, in book and quill pages, in the anvil rename field, in world creation fields and in the server address box.
Copying a block you are looking at
In creative mode, the middle mouse button picks the block you are aiming at and puts it in your hotbar. Hold Control while doing it on Java and you also copy the block’s data, including the contents of a chest or the settings on a redstone component. This is the closest thing to copy and paste for actual blocks in vanilla.
Copying coordinates and commands
On Java you can copy your current coordinates straight to the clipboard from the debug screen. Open it and use the copy-location key combination, then paste the result into chat or into a coordinate converter such as the nether portal calculator.
Special characters and colour codes
The section sign used by colour codes cannot be typed on most keyboards, so pasting it is the normal way to use it. Copy the code you need from our colour codes page, or build a whole coloured string with the colour text generator and paste the finished result into your config or MOTD.
Books, signs and long text
Book and quill accepts pasted text, which is the easiest way to write anything long — type it outside the game and paste it in a page at a time. Signs accept paste too, but only up to the character limit per line, and anything beyond that is silently dropped.