About this tool
Diff Checker is a free online tool that compares two texts and highlights the differences. It supports line-by-line and word-by-word comparison, side-by-side and unified views, and ignore-case / ignore-whitespace options. Everything runs locally in your browser.
How it works
1
Paste the original text
Type or paste the original text in the left panel. You can also drop a .txt file into the drop zone.
2
Paste the changed text
Paste the modified version in the right panel. The diff updates live as you type.
3
Review differences
Removed lines are highlighted red, added lines green, and changed lines yellow with word-level highlights. Toggle side-by-side or unified view, and copy the result.
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Frequently Asked Questions
What diff algorithm is used? v
The tool uses the Myers diff algorithm - the same algorithm used by Git. It is fast, produces minimal diffs, and works well for most cases.
What is the difference between side-by-side and unified view? v
Side-by-side shows the two texts in parallel columns with aligned lines. Unified view shows a single column where removed lines are prefixed with a minus and added lines with a plus - the same format as Git diff output.
Are my texts sent to a server? v
No. Everything is processed locally in your browser. No texts, files, or results leave your device.
What does 'ignore whitespace' do? v
It treats lines that differ only in leading or trailing whitespace (or line endings) as identical. Useful when comparing code that was reformatted without changing logic.