Diff Tools Compared: How to Find Differences in Text and Code

What is a Diff?

A "diff" shows the differences between two pieces of text. It's named after the Unix diff command. Diffs are fundamental to version control, code review, and debugging.

Types of Diff Views

Unified diff

Changes shown in a single view with + and - prefixes:

-const greeting = "Hello"
+const greeting = "Hello, World"
 console.log(greeting)

Split/Side-by-side diff

Two panels showing old and new versions side by side - easier to read for larger changes.

Command Line diff

# Basic diff
diff file1.txt file2.txt

# Unified format (git-style)
diff -u file1.txt file2.txt

# Recursive directory diff
diff -r dir1/ dir2/

Git Diff

# Unstaged changes
git diff

# Staged changes
git diff --staged

# Between branches
git diff main..feature-branch

# Specific file
git diff HEAD~1 src/app.js

When to Use Which Tool

Scenario	Best tool
Quick text comparison	Online Diff Checker
Code review	GitHub/GitLab PR view
Local code changes	VS Code built-in diff
Config file comparison	diff command
Production debugging	git diff

VS Code Diff

1. Select two files in Explorer
2. Right-click → "Compare Selected"
3. Or: code --diff file1 file2

Try our Diff Checker for quick side-by-side or unified text comparison.