How do I apply a recorded macro to a range of lines without re-recording it in Vim?

Explanation

The :[range]normal @a command runs a recorded macro against every line in a given range. Unlike 5@a, which repeats a macro a fixed number of times from the cursor position, :normal @a with a range applies the macro independently to each line in that range — ideal when you know exactly which lines need transforming.

How it works

• :[range] — an Ex range such as 1,10, '<,'> (visual selection), % (entire file), or .,$ (current line to end)
• normal — execute normal-mode keystrokes on each line in the range
• @a — replay the macro stored in register a

Vim positions the cursor at the start of each line before executing the macro, so the macro should be written assuming cursor-at-line-start positioning.

Example

Suppose register a contains I// <Esc> (prepend // to a line). After recording it with qa I// <Esc>q, you can comment out lines 5 through 20:

:5,20normal @a

Or apply it to a visual selection:

:'<,'>normal @a

Or to the entire file:

:%normal @a

Tips

• Use normal! instead of normal to ignore user-defined mappings and ensure raw Vim behavior
• If the macro uses motions that could fail on some lines (e.g., searching for a pattern not on every line), wrap it defensively or use :silent! :[range]normal @a to suppress errors
• You can use any register: @b, @q, etc.
• Combine with :g/pattern/normal @a to apply the macro only to lines matching a pattern