Completion is enabled by default (to disable it, use M-x customize-variable RET erc-modules).

Nick Completion

You can complete on all channel members using TAB.

There are two modules to achieve this:

Use the old style only if you do not have pcomplete on your system.

Command Completion

Completion also works with ErcCommands.

New Style

Enabled by default.

Old Style

Old style completion had a feature that was never used: You could reduce completion to you pals only (maybe this was supposed to be useful on very full channels such as #debian). In order to use it, set the variable ‘erc-nick-completion’.

You can set it to either ‘all, ‘pals, or a function named ‘erc-nick-completion-exclude-myself’ to determine what the list of possible completions look like. Of course you can also write your own function to provide a list of possible completions. This is no longer supported in the new-style completion.