Diff Checker
Free online Diff Checker tool.
About Diff Checker
Free online Diff Checker tool.
Diff Checker compares two blocks of text or code and highlights exactly what changed. Paste the original on the left and the revised version on the right, then the tool marks added lines in green, removed lines in red and modified passages inline, with a word level mode available for shorter strings. It can ignore whitespace and letter case, displays line numbers, and produces unified diff output that you can copy into a pull request or bug report. Developers use Diff Checker to review configuration changes, editors to compare draft revisions, and students to check two versions of an answer. The comparison runs in your browser, needs no account, and your documents are never stored.
How to Use Diff Checker
- Paste or type your text into the editor.
- Watch the stats or output update instantly as you type.
- Adjust any options (case, delimiters, formatting) if needed.
- Copy the result with one click when you are done.
Key Features
- Live output on every keystroke — no submit button to wait for.
- Handles essays, articles and long documents with ease.
- One-click copy for the finished text or statistics.
Frequently Asked Questions
Can Diff Checker ignore whitespace and letter case differences?
Yes. Enable ignore whitespace to skip indentation, tabs and extra spaces, and enable ignore case to treat uppercase and lowercase as equal, which is useful when the only change is formatting. The tool still shows line numbers and the unified output, so you can copy a clean patch. For long documents, switch to word level comparison to see the exact phrase that changed instead of reading through the whole line.
Is Diff Checker free to use?
Yes. Diff Checker is completely free with unlimited use — no account, download or payment required.
Is my data uploaded to a server?
No. Diff Checker runs entirely in your browser. Your inputs are never sent to our servers or stored anywhere.
Does Diff Checker work on mobile?
Yes. The interface is fully responsive and works in any modern browser on Android, iPhone, tablets and desktops.
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