Text Diff Checker — Free Online Tool
Compare two texts and see exactly which lines were added or removed.
About Text Diff Checker
The Text Diff Checker compares two blocks of text line by line and highlights exactly what changed between them. Added lines are shown in green and removed lines in red, so you can spot edits in documents, code, configuration files, or contracts in seconds without reading every word.
Built on an efficient longest-common-subsequence algorithm, the comparison runs entirely in your browser. Nothing you paste is uploaded or stored anywhere, which makes it safe for reviewing sensitive drafts, private notes, or proprietary source code.
How to Use Text Diff Checker
- Paste the original version into the left box labeled Original Text.
- Paste the updated version into the right box labeled Changed Text.
- Click 'Compare Texts' to generate the line-by-line difference.
- Review the green additions and red deletions, plus the summary count at the top.
Key Features
Side-by-side input with clear line-by-line difference output
Added and removed lines color-coded in green and red
Summary count showing how many lines were added and removed
Accurate matching powered by a longest-common-subsequence algorithm
100% client-side processing so your text never leaves your device
No signup, no limits, and no watermarks
Frequently Asked Questions
How does the diff checker compare two texts?
It splits both inputs into lines and uses a longest-common-subsequence algorithm to find the smallest set of additions and deletions that turns the original into the changed version. Matching lines are shown in gray, additions in green, and removals in red.
Does this tool compare word by word or line by line?
The comparison works at the line level, which is ideal for documents, lists, and code. A line that has any change is shown as one removed line and one added line.
Is my text uploaded to a server?
No. The entire comparison happens locally in your browser using JavaScript, so your content stays private on your own device.
Can I compare code or configuration files?
Yes. Just paste both versions into the boxes. Because matching is line-based, it works well for source code, JSON, YAML, and plain text alike.