Compare Code Versions Online — Use a Diff Checker for Code Reviews

Code review would be impossible without diffing. Whether you're reviewing a pull request, checking what changed between two versions of a config file, or comparing your local changes against what's deployed, a good diff view is what makes it manageable.

What a code diff shows

A diff tool compares two versions of text line by line and marks what changed. The standard format shows:

• Lines only in the first version (removed) — typically shown in red
• Lines only in the second version (added) — typically shown in green
• Lines present in both (unchanged) — shown in gray for context

Most modern diff tools also show inline character-level differences within changed lines, making it easier to spot small edits like a changed variable name or a flipped boolean.

Common scenarios where online diffing helps

The most common use case I see: you're debugging a production issue and you want to compare the deployed config to what's in version control. You copy both versions and paste them into a diff tool. In 10 seconds you know exactly what's different.

Another common one: comparing the output of two versions of a function. Run both, copy the outputs, diff them. Immediately see what changed.

Diffing in Git

# Diff working directory against last commit
git diff

# Diff two commits
git diff abc123 def456

# Diff two branches
git diff main feature/new-auth

# Diff a specific file between commits
git diff abc123 def456 -- src/auth.js

# Word-level diff (shows character changes within lines)
git diff --word-diff

Diffing in the terminal without Git

# Basic diff
diff file1.txt file2.txt

# Unified format (more readable, what Git uses)
diff -u file1.txt file2.txt

# Side-by-side comparison
diff -y file1.txt file2.txt

# Ignore whitespace differences
diff -w file1.txt file2.txt

When browser-based diffing is better

For quick comparisons without a Git repo, pasting text into an online diff tool is faster than any command-line setup. Use our Diff Checker to compare any two code snippets, configs, or text files in seconds.