Inline vs Side-by-Side Diff — Which View to Use and When

Every diff tool offers at least two viewing modes: inline (unified) and side-by-side (split). They show the same information differently — and choosing the right one can make code review and debugging significantly faster.

What Is Inline (Unified) Diff?

Inline diff shows both old and new content in a single column. Removed lines are highlighted in red, added lines in green, and unchanged lines provide context:

  function greet(name) {
-   return "Hello, " + name;
+   return `Hello, ${name}!`;
  }

This is the format used by git diff, GitHub pull requests (by default), and most CLI tools.

When Inline Works Best

• Small, scattered changes — When edits are spread across a large file, inline keeps context compact
• Reviewing logic changes — You can read the flow top-to-bottom like normal code
• Narrow screens — Mobile, small monitors, or embedded diff widgets
• Line additions/deletions — When lines are added or removed (not modified), inline is clearer

What Is Side-by-Side (Split) Diff?

Side-by-side diff shows the original on the left and the modified version on the right, aligned line-by-line:

LEFT (Original)              RIGHT (Modified)
function greet(name) {       function greet(name) {
  return "Hello, " + name;     return `Hello, ${name}!`;
}                            }

When Side-by-Side Works Best

• Character-level changes — Spotting small typos, variable renames, or parameter changes
• Refactoring review — When lines are restructured but logic is similar
• Wide screens — Takes advantage of screen real estate
• Document comparison — Non-code text where line alignment matters

Head-to-Head Comparison

Pro Tips for Code Review

1. Start with inline for an overview of what changed
2. Switch to side-by-side when you need to carefully compare specific sections
3. Use character-level highlighting (available in DiffSnap and most modern tools) regardless of view mode
4. Set your default based on your monitor — ultrawide users often prefer side-by-side

How Different Tools Handle It

• GitHub — Toggle between "Unified" and "Split" in PR file views
• VS Code — Click the split icon in the diff editor toolbar
• git diff — Use --word-diff for inline word-level, or pipe to delta/diff-so-fancy for prettier output
• DiffSnap — One-click toggle between inline and side-by-side, with character-level highlighting in both modes