Text Diff Checker
Paste two texts and instantly see every difference highlighted
Why Use Our Text Diff Checker?
Side by Side View
Compare original and modified text in two aligned columns for easy visual comparison.
Line by Line Diff
See which lines were added, removed, or changed with clear color-coded highlighting.
Character Level Diff
Pinpoint exact character changes within modified lines for precise editing.
100% Private
All processing happens in your browser. Your text never leaves your device.
What Is a Text Diff Checker?
A text diff checker is a software tool that compares two pieces of text and identifies the differences between them. It highlights additions, deletions, and modifications so you can quickly see exactly what changed. This is invaluable for developers reviewing code changes, writers comparing document revisions, and anyone who needs to track text edits accurately.
How Does This Diff Tool Work?
Our text diff checker uses the Longest Common Subsequence (LCS) algorithm, a well-established method in computer science for finding the differences between two sequences. Here is how it works step by step:
- The tool splits both input texts into individual lines.
- The LCS algorithm computes the longest sequence of lines that appear in both texts in the same order.
- Lines that exist in the original but not in the modified text are marked as removed (shown with a red background).
- Lines that exist in the modified text but not in the original are marked as added (shown with a green background).
- Lines present in both are marked as unchanged.
- For lines that are similar but not identical, a character-level diff highlights the exact characters that changed.
Common Use Cases for a Diff Checker
Text diff tools are used across many industries and workflows:
- Software Development: Compare code snippets, configuration files, or documentation before and after edits to identify bugs or unintended changes.
- Writing and Editing: Track revisions in essays, articles, or manuscripts to see what was added or removed between drafts.
- Legal and Compliance: Compare contract versions to quickly spot changes in terms, clauses, or conditions.
- Data Verification: Compare CSV output, log files, or structured data to find discrepancies between expected and actual results.
- Education: Students and teachers can use diff tools to check submitted work against source material or to learn about algorithms.
Is This Tool Private?
Yes. All text comparison happens entirely in your web browser using JavaScript. No data is uploaded to any server. This means your sensitive documents, source code, and personal text remain completely private and secure at all times. You can safely use this tool with confidential material.
Tips for Getting the Best Results
- Ensure both texts use the same line endings (our tool handles both Windows and Unix line endings automatically).
- For very large texts, the comparison may take a moment. The tool processes everything locally in your browser.
- Use the Clear button to reset both fields and start a new comparison.
- Character-level highlighting makes it easy to spot single-character typos or small edits within a line.