Text Diff Checker — Compare Two Texts Online Free
Paste any two texts and every difference is highlighted instantly — additions in green, deletions in red. This diff checker runs entirely in your browser: no server uploads, no account, no stored data. Your text stays on your device.
Whether you're a developer reviewing code changes, a lawyer comparing contract drafts, or a writer tracking edits across manuscript revisions, the tool adapts to your workflow through three comparison modes: word-level, line-level, and character-level.
How to Use the Text Diff Checker
- Paste your original text into the left panel.
- Paste the updated or modified text into the right panel.
- Read the result — differences are highlighted immediately as you type, with the navigation buttons letting you jump between change groups.
Use Split view to see both versions side by side (ideal for prose, contracts, and code). Switch to Unified view for a linear diff with + and − prefixes, the same format produced by git diff.
Keyboard shortcuts: Alt+↓ jumps to the next difference, Alt+↑ goes back, Shift+Enter copies the diff to clipboard.
What Is a Diff Checker?
A diff checker compares two versions of a text and highlights every difference between them. The term comes from the Unix diff command, a tool used in software development for decades to track changes between file versions. Today, text diff tools are used well beyond code: writers compare manuscript drafts, lawyers compare contract revisions, students check essay iterations, and translators verify source alignment.
This tool uses the Myers Diff Algorithm — the same algorithm behind Git — to detect additions, deletions, and modifications at the word or line level. Every change is color-coded: green for content added in the new version, red for content removed. Unchanged text stays neutral so your eye goes directly to what matters.
Three comparison modes adapt to different use cases: word-level (best for prose, articles, and legal text), line-level (best for code and structured content), and character-level (best for catching subtle typos or punctuation changes).
Common Use Cases
- Code review: Compare two versions of a function, configuration file, or API response to spot what changed before merging a pull request.
- Contract comparison: Detect unauthorized clause changes between consecutive contract drafts — faster and more reliable than reading both versions manually.
- Editorial workflow: See exactly which words an editor changed in your manuscript without relying on tracked-changes features in a word processor.
- Translation verification: Place source text on the left and translation on the right to quickly spot missing passages or structural deviations.
- QA and DevOps: Compare staging vs. production configs, database exports, or log file snapshots to identify environment-specific differences.
Frequently Asked Questions
What is a diff checker and when should I use one?
A diff checker compares two versions of a text and shows every difference in a color-coded view — additions, deletions, and modifications clearly marked. Use it any time you need to answer "what changed?" between two versions of a document: code, contracts, essays, config files, or any plain text.
Is my text safe when I use this diff checker?
Yes. The tool runs entirely in your browser using JavaScript — your text is never sent to a server, stored, or logged. You can safely use it with sensitive documents such as proprietary source code, contracts, or confidential business text. Nothing ever leaves your device.
What is the difference between word-level and line-level comparison?
Word-level comparison highlights individual words that changed, making it ideal for prose, articles, and contract text where exact wording matters. Line-level comparison flags entire lines as added or removed, which is more useful for code, configuration files, and structured data where changes typically happen at the line level — matching how git diff displays results.
Can I compare source code with this tool?
Yes. The diff checker works with any plain text, including source code in any language — Python, JavaScript, TypeScript, CSS, SQL, YAML, JSON, Go, and more. Use line-level mode for code to see changes the same way git diff shows them, with full-line highlighting and +/− prefixes in unified view.
Does this diff checker detect plagiarism?
It can identify identical or very similar passages between two specific documents you provide. However, it only compares the two texts you paste — it does not search the internet or academic databases. For comprehensive plagiarism detection across a large corpus, a dedicated plagiarism checker is more appropriate.
Resources
- Myers, E. W. — "An O(ND) Difference Algorithm and Its Applications" (1986) — The original paper describing the algorithm used in Git and most modern diff tools.
- Git Documentation — git-diff — Official documentation for Git's diff command, which uses the same algorithm as this tool.
