Text Diff Checker Online
Compare two texts side by side and highlight every addition and deletion. Powered by the LCS algorithm — the same method used by Git diff.
What is Text Diff Checker?
A Text Diff Checker is a tool that compares two versions of text and highlights the differences between them. It shows which lines were added, which were removed, and which remained unchanged — making it easy to review changes without manually scanning through both versions line by line.
Diff tools are essential in software development for code reviews, reviewing configuration changes, comparing documentation drafts, checking what changed between two API responses, and many other tasks. The classic diff format highlights deletions in red and additions in green, matching the output of commands like git diff on the command line.
This Text Diff Checker uses the Longest Common Subsequence (LCS) algorithm to compute the minimum edit distance between two texts. The result is the most concise representation of differences — showing only what genuinely changed, not just anything that looks different. It works on any plain text content: source code, prose, JSON, YAML, CSV files, or anything else you can paste into a text box.
How to Use
- 1
Paste the original text
Paste your original text, code, or document content into the left 'Original' panel.
- 2
Paste the modified text
Paste the updated version into the right 'Modified' panel. Click 'Load Sample' to see an example.
- 3
Click Compare
Click the "Compare" button to run the diff. Lines added in the modified version appear in green, removed lines in red, and unchanged lines in gray.
Features
- Line-by-line diff using the LCS algorithm
- Green highlights for added lines, red for removed
- Summary stats: lines added, removed, unchanged
- Line numbers for easy reference
- Handles code, prose, JSON, CSV, and any text
- Works entirely in your browser — 100% private
- No data sent to any server
- Free with no sign-up required
Frequently Asked Questions
- QWhat algorithm does this diff tool use?
- The tool uses the Longest Common Subsequence (LCS) algorithm to identify the minimal set of additions and deletions needed to transform the original text into the modified version. This is the same approach used by tools like Git diff.
- QCan I compare source code?
- Yes. The diff tool works on any plain text content — JavaScript, Python, TypeScript, JSON, YAML, HTML, CSS, configuration files, or any other text format. It compares text line by line.
- QIs there a size limit?
- The tool supports up to 300 lines per input for performance reasons. For larger files, consider using a command-line diff tool or a dedicated code review platform.
- QIs my text kept private?
- Yes. All comparison processing happens entirely in your browser using JavaScript. Your text is never sent to any server or stored anywhere.
- QDoes the diff ignore whitespace?
- Currently, the diff is whitespace-sensitive, meaning extra spaces or different indentation will show as changes. Future versions may add a whitespace-ignore option.
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