How do I count the number of pattern matches in a file without making substitutions?

Explanation

The :s///gn command counts how many times a pattern appears in the file without actually replacing anything. The n flag suppresses the substitution and instead reports the match count, making it a quick way to audit your file before committing to a large :substitute operation.

How it works

• :s/pattern// is the substitute command with an empty replacement
• g makes it global (count all matches on each line, not just the first)
• n suppresses the actual substitution and prints the count instead

Combine with a range to scope the count:

• :%s/pattern//gn — count across the whole file
• :'<,'>s/pattern//gn — count within a visual selection
• :5,20s/pattern//gn — count within a line range

Example

You want to know how many TODO comments are in a file:

:%s/TODO//gn

Vim prints:

14 matches on 11 lines

No changes are made to the buffer. The message tells you both the total match count and how many lines contain the pattern.

Tips

• Combine with \c for case-insensitive counting: :%s/\ctodo//gn
• Use n alone (without g) to count only the first match per line: :%s/pattern//n
• This works with the full power of Vim's regex engine, so complex patterns are fine: :%s/\v^\s*#.*//gn counts comment lines
• The last search pattern is updated, so pressing n afterward will jump through matches