Free Online Text Diff Checker and Compare Tool
Comparing two versions of text to find what changed is a daily task for writers, developers, lawyers, and data professionals. Manually scanning two documents side by side is slow and error-prone — especially with long files where a single character change can be easy to miss. Our free text diff checker highlights additions in green, deletions in red, and modifications with clear visual contrast using Google's diff-match-patch library.
Upload .txt files directly or paste text into two side-by-side input areas. A stats summary shows total changes, additions, and deletions at a glance. Use the swap button to quickly reverse the comparison direction. Everything runs in your browser — your documents never leave your device. Whether you are reviewing a contract revision, validating a config change, or proofreading an article edit, this tool surfaces every difference in seconds.
How to Use the Text Diff Checker
Paste your original text into the Text A input area and the revised text into Text B, or click Upload .txt on either side to load files from your device. The diff generates automatically as you type or after uploading. Additions appear highlighted in green, deletions in red, and unchanged text displays normally. Review the stats bar for a quick count of total changes, additions, and deletions. Use the Swap button to reverse Text A and Text B if you entered them in the wrong order. Copy the diff summary to your clipboard for sharing or documentation.
Who Uses a Text Diff Checker?
- Writers and editors compare article drafts to see exactly what changed between revisions.
- Software developers review code snippets, configuration files, and API responses for differences.
- Legal professionals compare contract versions to identify modified clauses and terms.
- Data analysts validate that data exports and transformations produced the expected output.
- SEO specialists track competitor content changes and monitor webpage modifications over time.
- Students compare essay drafts and verify that revisions address feedback correctly.
- Translators compare original and translated text to ensure nothing was omitted or altered.
Key Features
- Color-coded diff: green for additions, red for deletions
- Upload .txt files on either or both input sides
- Swap button to reverse comparison direction instantly
- Stats summary showing total changes, additions, and deletions
- Powered by Google's diff-match-patch (Myers diff algorithm)
- 100% browser-based — text never leaves your device
Tips for Effective Text Comparison
Normalize whitespace before comparing if formatting differences are not important — trailing spaces and tab-vs-space differences can create noise in the diff output. For code comparison, ensure both snippets use the same indentation style for cleaner results. The tool compares plain text only — for rich text or formatted documents, convert to plain text first. For very large files exceeding 500,000 characters, command-line tools like diff or git diff may be more practical. Save the diff output as HTML if you need to share color-coded results with colleagues. When comparing configuration files, sort keys alphabetically in both versions first to reduce noise from reordering that is not a meaningful change. Use the stats bar to quickly assess whether a revision is a minor tweak or a substantial rewrite before reading every highlighted line.
Frequently Asked Questions
How does the diff algorithm work?
Google's diff-match-patch uses the Myers diff algorithm to find the minimum edit distance between two texts. It groups adjacent changes together for readability, so you see coherent blocks of additions and deletions rather than character-by-character noise.
Can I upload files instead of pasting?
Yes. Each text input has an Upload .txt button that loads a file from your device. You can upload files on one or both sides. You can also swap Text A and Text B with one click if you entered them in the wrong order.
Is there a size limit?
Texts up to 500,000 characters each work well in modern browsers. For very large files such as full codebase dumps, command-line tools like diff, git diff, or Meld are more practical.
Can I download the diff results?
Copy the diff summary to your clipboard for sharing via email or chat. To preserve color coding, save the browser output as HTML or take a screenshot of the highlighted diff panel.
Does it compare line by line or word by word?
The diff-match-patch algorithm operates at the character level but groups adjacent changes into readable blocks. This means you see word-level and line-level changes clearly highlighted rather than individual character diffs.
Is my text uploaded to a server?
No. Comparison runs entirely in your browser. Your text, code, and documents stay on your device and are never transmitted anywhere.
Can I compare code or JSON files?
Yes. Paste any plain text including source code, JSON, YAML, XML, or configuration files. The diff algorithm treats all input as plain text and highlights every character-level change regardless of the content type.