How do I group regex atoms in Vim without creating a backreference?

Explanation

In Vim's regex engine, \( and \) create a capturing group whose contents are stored in \1, \2, etc. and can affect performance. \%( and \%) create a non-capturing group — it groups atoms for alternation or quantifiers without the overhead of storing the match.

How it works

• \%(pattern\) — group pattern for operator precedence or alternation, without storing the submatch
• Use this whenever you don't need a backreference in the replacement or a later part of the pattern
• Non-capturing groups are faster in searches with many repetitions because Vim doesn't track what matched inside them

Example

Match lines ending with foo or bar without a backreference:

/\%(foo\|bar\)$

Compare with a capturing version (identical match, but stores the result in \1):

/\(foo\|bar\)$

Using \%(\) for alternation inside a larger substitution:

:%s/\%(https\|http\):\/\//URL: /g

This matches both https:// and http:// and replaces them with URL: , without using a backreference that could conflict with \1 used elsewhere in the pattern.

Tips

• In \v (very magic) mode, %( and ) work as non-capturing groups without backslashes: /\v%(foo|bar)$
• Prefer \%(\) over \(\) when building complex patterns with :substitute if you only need grouping for alternation or quantifiers
• Numbered captures \1–\9 are only counted from capturing groups; inserting a non-capturing group does not shift the numbering