How to Compare Two Texts Online: Find Every Difference Instantly

Text comparison (diff) tools show exactly what changed between two versions of text — word by word, line by line. Whether you're reviewing document revisions, comparing code versions, or checking for plagiarism, a diff tool saves hours of manual review.

How Diff Algorithms Work

Most diff tools use the Myers diff algorithm (1986, still the standard). It finds the shortest sequence of insertions and deletions that transforms text A into text B. Additions are shown in green; deletions in red; unchanged lines in grey. Word-level diff also highlights the specific words that changed within a line.

Use Cases

• Document review: Compare original and edited contracts to see what legal terms changed
• Code review: See what changed between two versions of a function (Git does this automatically)
• Content comparison: Compare two versions of an article to spot unauthorized changes
• Configuration files: See what changed between working and broken config files
• API responses: Compare expected vs actual JSON responses in testing

Side-by-Side vs Unified Diff

• Side-by-side: Original and modified shown in two columns. Best for long documents where you want to see context around changes.
• Unified diff: Single column with additions (+) and deletions (−) interleaved. Standard format in Git. More compact.

Ignoring Whitespace and Case

Good diff tools allow you to ignore whitespace changes (an extra space shouldn't count as a difference) and optionally ignore case differences. This reduces noise and focuses the comparison on meaningful content changes.

Compare any two texts with our Text Comparison tool.