How do I search and replace text across an entire file?

Explanation

The :%s/old/new/g command replaces all occurrences of old with new across every line in the file.

How it works

• : enters command-line mode
• % means "every line in the file"
• s is the substitute command
• /old/new/ specifies the search pattern and replacement
• g flag means "all occurrences on each line" (without it, only the first match per line is replaced)

Example

Given the text:

foo bar foo
foo baz foo

Running :%s/foo/qux/g results in:

qux bar qux
qux baz qux

Tips

• Add c flag for confirmation: :%s/old/new/gc prompts before each replacement
• Add i flag for case-insensitive: :%s/old/new/gi
• Use \< and \> for whole-word matching: :%s/\<old\>/new/g
• Replace only in a visual selection by selecting text first, then typing :s/old/new/g