The Free Diff Checker
Paste two versions of any text or code and see exactly what changed — line by line, color-coded in your browser. No server, no signup, no limits.
Compare Texts
Client-side only · nothing is transmitted · your text stays in the browser
What is a diff checker?
A diff checker compares two versions of a text and highlights every line that was added, removed or left unchanged. The word diff comes from the Unix diff command, a staple of software development since the 1970s.
This tool runs entirely in your browser using Vanilla JavaScript. You paste two text blocks, hit Compare, and the result appears instantly — color-coded green for additions and red for removals. No data leaves your device.
+ This line was added in the second version - This line was removed from the original This line is unchanged
How to use this diff checker
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1
Paste the original text
Put your original content — code, markdown, config, prose — in the left text area.
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2
Paste the changed text
Put the modified version in the right text area.
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3
Click Compare
Hit the Compare button. The diff output appears below, color-coded line by line.
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4
Read the result
Green lines (+ prefix) are new. Red lines (- prefix) were removed. Neutral lines are unchanged.
Frequently asked questions
What is a diff checker? +
A diff checker compares two texts and highlights what was added, removed, or changed between them.
Does it work with code? +
Yes. It handles any plain text including code, configuration files, markdown and more.
Is my text sent to a server? +
No. All comparison happens in your browser. Nothing is transmitted.
What do the colors mean? +
Green lines were added in the second text. Red lines were removed. Unchanged lines are shown without highlighting.