Tab completion in minibuffer: case insensitive

Question

When the minibuffer offers tab completion, how can I make that case-insensitive?

Preferably a global setting that makes any completion – a filename, a command, ido, etc. – obey that setting.

Answer 1

Sure. Set variable completion-ignore-case to t. Put this in your init file:

(setq completion-ignore-case  t)

C-h v completion-ignore-case:

completion-ignore-case is a variable defined in C source code.

Its value is nil

Documentation:

Non-nil means don't consider case significant in completion.

For file-name completion, read-file-name-completion-ignore-case controls the behavior, rather than this variable.

For buffer name completion, read-buffer-completion-ignore-case controls the behavior, rather than this variable.