How do I compare the current buffer to another file using Vim's built-in diff mode without leaving the editor?

Explanation

:diffsplit {file} opens a file in a horizontal split and immediately activates diff mode, highlighting the differences between both buffers. It combines :split and :diffthis into a single command, making file comparison fast and seamless without leaving Vim.

How it works

• :diffsplit {file} — open {file} in a horizontal split and enable diff highlighting on both windows
• :vert diffsplit {file} — use a vertical (side-by-side) split, which is usually more readable on wide terminals
• Vim uses the diff, diffadd, and diffchange highlight groups to color the changed regions

Navigating the diff

Once in diff mode, these commands let you work through the changes:

• ]c — jump to the next diff hunk
• [c — jump to the previous diff hunk
• dp — diff put: push the current hunk from this window to the other
• do — diff obtain: pull the change from the other window into this one
• :diffupdate — re-diff both buffers after making manual edits

Example

Compare a configuration file against a known-good backup:

:vert diffsplit ~/.config/nvim/init.vim.bak

Vim opens a side-by-side view with changed lines highlighted and ]c / [c ready to jump between differences.

Tips

• Exit diff mode with :diffoff! to restore normal display across all windows
• For three-way merges, open three splits and run :diffthis in each manually
• Starting from the shell, vimdiff file1 file2 is equivalent to opening the first file and running :vert diffsplit file2