Text Diff Checker
Comparing two versions of a document by eye is tedious and error-prone. Our free Text Diff Checker uses a Longest Common Subsequence algorithm to compare your original and modified text line by line, highlighting every addition in green and every deletion in red. Unchanged lines are displayed without highlighting so differences stand out immediately. Summary cards show the total count of lines added, removed, and unchanged, giving you a quick overview of how much changed. This tool is perfect for reviewing edits to articles, comparing code revisions, or verifying contract modifications. For finding and replacing specific text patterns, try the Find and Replace tool. All processing happens in your browser with nothing uploaded or stored, so your content stays private. Paste your two versions, click Compare, and see every difference highlighted instantly. If you need to clean up extra whitespace before comparing, run your text through the Remove Extra Spaces tool first.
How to Use This Tool
- Paste the original text into the left editor.
- Paste the modified text into the right editor.
- Click the "Compare" button to generate the diff.
- Review the color-coded results: green for additions, red for deletions, no highlight for unchanged lines.
Examples
| Use Case | Original | Modified | Result |
|---|---|---|---|
| Word change | The quick brown fox | The fast brown fox | 1 removed, 1 added |
| Line added | Line 1\nLine 2 | Line 1\nNew line\nLine 2 | 1 added, 0 removed |
| Identical | Same text | Same text | 0 changes |
What This Tool Is Useful For
- Reviewing edits made by collaborators, editors, or AI writing assistants.
- Comparing code versions when you do not have access to a Git diff tool.
- Verifying changes in legal contracts, policies, or terms of service.
- Checking translation updates by comparing original and revised text.
- Debugging configuration files by spotting unintended changes between versions.
Frequently Asked Questions
- How does the diff algorithm work?
- The tool uses a Longest Common Subsequence (LCS) algorithm to compare the two texts line by line. It identifies which lines are unchanged, which were added in the modified text, and which were removed from the original. This is the same fundamental approach used by version control systems like Git.
- What do the colors mean?
- Green lines with a + prefix indicate additions — lines present in the modified text but not in the original. Red lines with a - prefix indicate deletions — lines present in the original but not in the modified text. Unmarked lines with no highlight are unchanged between the two versions.
- Can I compare code with this tool?
- Yes. The diff display uses a monospace font and preserves whitespace, making it suitable for comparing code, configuration files, JSON, and other structured text. For very large files, keep in mind that processing happens in your browser so performance depends on your device.
- Is there a size limit?
- There is no hard limit since all processing happens locally. However, the LCS algorithm has quadratic time complexity relative to the number of lines, so texts with thousands of lines may take a moment to process. For most practical comparisons (under 1,000 lines), the diff is instant.
- Is my data private?
- Yes. Both texts stay entirely in your browser. Nothing is sent to any server, making this tool safe for comparing confidential documents, proprietary code, and sensitive content.
More Text Tools
- All Text Tools — browse the full collection of text utilities
- Find and Replace — search and replace text with regex support
- Remove Extra Spaces — clean up whitespace before comparing
- Duplicate Line Remover — remove duplicate lines from your text
- Yantrasagaram homepage
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