Diff Checker
Compare two text blocks and see exactly what changed. Detect added, removed, and unchanged lines side by side instantly in your browser
TEXT
Original (A)
Modified (B)
Tip: paste text in both fields — differences appear automatically.
Runs 100% Locally in Your Browser
This tool processes your data entirely on your device. Nothing is uploaded, stored, or sent to any server.
No Uploads
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Secure by Default
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Frequently Asked Questions
What is a diff checker?
A diff checker compares two pieces of text and highlights the lines or characters that were added, removed, or unchanged between them.
How to compare two text blocks or files online?
Paste the original text in the left panel and the modified text in the right panel — differences are highlighted instantly.
What do the colours mean in the diff output?
Green highlights mark added lines, red marks removed lines, and unchanged lines appear without highlighting.
What is the difference between a line diff and a character diff?
A line diff compares whole lines; a character diff highlights the exact characters that changed within a line — more granular but harder to read at scale.
What algorithm does the diff checker use?
It uses the Longest Common Subsequence (LCS) algorithm, which finds the optimal set of line additions and removals to transform one text into the other.
Can I use the diff checker to compare code files?
Yes — paste any text including source code, configuration files, or documents and the tool will highlight the differences.
Is my text sent to a server for comparison?
No. Both text panels are compared locally in your browser — your content never leaves your device.