How do I swap or rearrange text using captured groups in Vim substitution?

Explanation

Vim's substitute command supports captured groups (back-references) using \( and \), allowing you to capture parts of a match and rearrange them in the replacement. This is one of the most powerful text transformation techniques in Vim.

How it works

• \(pattern\) — captures the matched text into a numbered group
• \1, \2, etc. — refers to the captured groups in the replacement
• Groups are numbered left-to-right by their opening parenthesis
• Up to 9 groups (\1 through \9) are supported

Example

Swap first and last names:

:%s/\(\w\+\) \(\w\+\)/\2 \1/g

Before: John Smith
After:  Smith John

Reformat a date:

:%s/\(\d\{4}\)-\(\d\{2}\)-\(\d\{2}\)/\3\/\2\/\1/g

Before: 2024-01-15
After:  15/01/2024

Tips

• Use \v (very magic) for cleaner syntax: :%s/\v(\w+) (\w+)/\2 \1/g
• \0 or & refers to the entire match
• Non-capturing groups \%(pattern\) group without capturing, preserving group numbers