Diff Checker

About Diff Checker

The Diff Checker is a free online text comparison tool that lets you find the exact differences between two blocks of text. It highlights additions, deletions, and modifications at both the line level and character level, making it easy to see precisely what changed between two versions of a document, piece of code, or any other text content.

How to Use the Diff Checker

1. Paste the original text — Copy and paste the original version of your text into the left text area labeled "Original Text." You can also try a quick example to see how it works.
2. Paste the modified text — Copy and paste the updated version into the right text area labeled "Modified Text." Use the swap button (⇄) if you need to switch them.
3. Set comparison options — Enable "Ignore whitespace" to skip spacing differences, "Ignore case" for case-insensitive comparison, or "Trim lines" to ignore leading/trailing spaces on each line.
4. Click Compare Texts — Click the button to generate the diff report. The tool will analyze both texts and identify all differences.
5. Review the results — Browse the color-coded diff output. Switch between side-by-side and unified views. Use the ↑ Prev / ↓ Next buttons to jump between changes.

Key Features

• Character-level highlighting — Within modified lines, the specific characters that changed are highlighted with darker shading, so you can see exactly what was altered.
• Side-by-side and unified views — Choose the view that works best for your workflow. Side-by-side shows both versions in parallel columns; unified shows a combined view similar to Git diff output.
• Similarity scoring — Get an instant percentage showing how similar the two texts are, using the Ratcliff/Obershelp pattern-matching algorithm.
• Smart comparison options — Ignore whitespace variations, case differences, or leading/trailing spaces to focus on the changes that matter.
• Change navigation — Jump between changes with the Previous/Next buttons, especially useful for long documents with scattered edits.
• Quick examples — Try built-in examples (code refactoring, document editing, config updates) to see the tool in action instantly.

Understanding the Diff Output

The diff output uses color coding to make differences easy to spot:

• Green rows indicate lines that were added in the modified text.
• Red rows indicate lines that were removed from the original text.
• Amber/yellow rows indicate lines that were modified — they exist in both versions but with changes.
• White rows indicate unchanged lines that are identical in both versions.

Within modified lines, character-level highlights pinpoint the exact characters that changed. Deleted characters appear with a red background and strikethrough, while added characters appear with a green background.

Common Use Cases

• Code review — Compare old and new versions of source code to review changes before merging.
• Document proofreading — See what your editor or collaborator changed in a document draft.
• Configuration management — Track changes between configuration file versions to prevent deployment issues.
• Content writing — Compare article revisions to see how the content evolved.
• Data validation — Verify that data exports or transformations produced the expected output.

Frequently Asked Questions

What is a diff checker?

A diff checker is a tool that compares two pieces of text and highlights the differences between them, showing which lines were added, removed, or modified.

What do the colors mean in the diff output?

Green highlights indicate added content, red highlights indicate removed content, and amber/yellow highlights indicate modified lines where some characters changed. Within modified lines, individual character changes are highlighted with darker shading.

What is the difference between side-by-side and unified views?

Side-by-side view shows the original and modified texts in parallel columns for easy visual comparison. Unified view combines both texts into a single column with added lines marked with + and removed lines marked with −, similar to the output of the Unix diff command.

Can I compare code with this diff checker?

Yes, the diff checker works with any plain text including source code, configuration files, documents, and data. It preserves indentation and whitespace, making it ideal for code comparisons.

What does the similarity percentage mean?

The similarity percentage indicates how much of the text content is shared between the two versions. A 100% similarity means the texts are identical, while 0% means they share no common content. It is calculated using the Ratcliff/Obershelp pattern-matching algorithm.