How do I create abbreviations for the Vim command line to fix typos like W and Q?

Explanation

:cnoreabbrev defines a non-recursive command-line abbreviation — like noremap but for Ex commands. The most practical use is silently correcting capital-letter typos (:W, :Q, :Wq) that Vim would otherwise reject as unknown commands.

How it works

• :cabbrev expands abbreviations recursively (like :map), which can cause unexpected behavior if the expansion also matches an abbreviation
• :cnoreabbrev expands non-recursively and is the safer choice
• Abbreviations are matched only at the start of a command and only when followed by a space, newline, or |

Example

Add these to your vimrc:

cnoreabbrev W  w
cnoreabbrev Q  q
cnoreabbrev Wq wq
cnoreabbrev WQ wq
cnoreabbrev Wa wa
cnoreabbrev QA qa

Now :W<CR> silently saves without an error, and :Wq<CR> saves and quits.

You can also create convenient shortcuts:

cnoreabbrev tn tabnew
cnoreabbrev th tabprev
cnoreabbrev tl tabnext

Tips

• Unlike iabbrev, command-line abbreviations only expand when the cursor is right after the abbreviation followed by a non-keyword character — no unintended mid-word expansion
• Check existing abbreviations with :cabbrev (no arguments) to list all defined ones
• To delete an abbreviation: :cunabbrev {lhs}