Diff Checker
Compare two texts side-by-side and find differences instantly with visual line and word highlights.
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Text Comparison
Paste text in both fields above to see the differences.
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How to Use the Diff Checker
Our free online diff checker helps you compare two pieces of text and instantly see the differences between them. Whether you're reviewing code changes, comparing document revisions, or checking configuration files, this tool makes it easy to spot every addition, deletion, and modification.
To get started, paste your original text in the left panel and the modified version in the right panel. The tool immediately computes the differences using a Longest Common Subsequence (LCS) algorithm — the same approach used by professional version control systems like Git.
The results are displayed in your choice of two views. Split view shows both texts side-by-side with color coding: green backgrounds highlight added lines, red backgrounds highlight removed lines, and unchanged lines appear normally. For changed lines, individual words that differ are highlighted with a deeper shade, making it easy to spot exactly what was modified within a line.
Unified view shows all changes in a single column, with line numbers for both the original and modified text. Added lines are marked with a + symbol and removed lines with a − symbol. This view is compact and similar to how Git displays diffs in the terminal.
The statistics bar above the output gives you a quick summary: total lines analyzed, lines added, lines removed, and unchanged lines. Toggle the Ignore whitespace option to focus on meaningful content changes and ignore differences in indentation or trailing spaces.
Try the sample texts to see how the tool works — we've included examples for code changes and prose edits. All processing happens client-side in your browser with zero server requests, so your data stays completely private.
Frequently Asked Questions
How does the diff checker work?
The diff checker uses a Longest Common Subsequence (LCS) algorithm to find the differences between two texts. It compares the texts line by line, identifying which lines were added, removed, or remain unchanged. For changed lines, it also performs word-level comparison to highlight exactly what changed within each line.
What is the difference between split view and unified view?
Split view shows the original and modified texts side by side, making it easy to see changes in context. Unified view shows all changes in a single column with + and − markers, similar to how Git displays diffs. Split view is better for comparing short texts, while unified view works well for longer documents.
Can I compare code files?
Yes! The diff checker works with any text content including source code, configuration files, CSV data, and prose. It preserves whitespace and formatting, displaying everything in a monospaced font. Use the 'Ignore whitespace' option if indentation changes aren't important to your comparison.
Is there a size limit?
The tool runs entirely in your browser, so it can handle texts of several thousand lines. For very large files (tens of thousands of lines), performance may slow down since the LCS algorithm needs to compare every line. For very large comparisons, consider using a desktop tool like VS Code's built-in diff viewer.
Is my text sent to a server?
No. All comparison processing happens entirely in your browser using JavaScript. Your text never leaves your device — there are no server requests, no uploads, and no data collection. The tool works offline and is completely private.