How do I force-convert all indentation including tabs in the middle of lines throughout an entire file?

Explanation

The :retab command converts leading whitespace according to the current tabstop and expandtab settings, but it only touches indentation at the start of lines. The ! flag extends this to ALL tab characters anywhere in the file — including those used for column alignment in the middle of a line.

How it works

• :retab — converts leading whitespace (tabs→spaces or spaces→tabs based on expandtab)
• :retab! — converts ALL whitespace that contains tabs, including inline tabs
• % — applies to the whole file
• The new whitespace uses the current tabstop value (set tabstop first if needed)

Example

A file with tabs used for column alignment:

Name\tAge\tCity
Alice\t30\tLondon
Bob\t25\tParis

After :set expandtab tabstop=4 | :%retab!:

Name    Age    City
Alice   30     London
Bob     25     Paris

With plain :retab (no !), the tabs in the middle of these lines would be left unchanged.

Tips

• Always set tabstop and expandtab (or noexpandtab) before running :%retab!
• To convert spaces back to tabs: :set noexpandtab tabstop=4 | :%retab!
• Use :'<,'>retab! to apply only to a visual selection
• Be cautious with source files — inline tabs in strings or heredocs may be intentional