How do I compare two files side by side using Vim's built-in diff mode?

Explanation

Vim has a built-in diff mode that highlights added, removed, and changed lines between two (or more) buffers. :vertical diffsplit opens a second file in a vertical split alongside the current buffer and enables diff highlighting for both.

How it works

• :vertical diffsplit {file} splits the window vertically and opens {file} in diff mode with the current buffer
• Changed lines are highlighted; folds collapse identical sections so only differences are visible
• Navigate between hunks with ]c (next change) and [c (previous change)
• :diffupdate refreshes the diff highlighting after making edits
• :diffoff (or :diffoff! for all windows) exits diff mode

You can also start Vim in diff mode from the shell:

vim -d file1 file2

Example

You have config.prod.yaml open and want to compare it with config.dev.yaml:

:vertical diffsplit config.dev.yaml

Both files appear side by side with differences highlighted. Press ]c to jump to the first differing section.

Tips

• :diffget (do) pulls a change from the other buffer into the current one
• :diffput (dp) pushes a change from the current buffer to the other one
• :windo diffthis enables diff mode for all currently open windows — useful when you have already opened both files manually
• For a horizontal split instead, use :diffsplit {file} (without vertical)