How do I prepend ascending numbers only to the lines in my visual selection?

Explanation

When you need quick numbered steps, logs, or checklist entries, this pattern adds numbers only to the lines you selected, not the whole buffer. It uses a visual range and an expression replacement, so the numbering is computed per matched line at execution time. This is especially useful for one-off formatting jobs where macros are overkill.

How it works

:'<,'>s/^/\=line('.')-line("'<")+1 . '. '/

• '<,'> targets only the last visual selection range
• s/^/.../ substitutes the start of each line
• \= tells :substitute to evaluate the replacement as a Vim expression
• line('.') is the current line being processed
• line("'<") is the first line of the visual selection
• Subtracting and adding 1 gives a 1-based counter
• . '. ' appends a period and trailing space after the number

Example

Before:

refactor parser
write migration
add regression test

Select those three lines in Visual Line mode, then run the command.

After:

1. refactor parser
2. write migration
3. add regression test

Tips

• For padded numbers, use printf('%02d. ', line('.')-line("'<")+1) in the expression
• To continue numbering from 10, replace +1 with +10