Free Text Diff Checker Online
Compare two texts line-by-line. Added lines in green, removed in red. Browser-only, no signup — perfect for sensitive documents.
Paste text in both boxes to see the line-by-line diff.
Line-by-line diff computed in your browser. Nothing is uploaded.
A text diff checker compares two pieces of text and highlights what changed. Notepad AI's diff tool uses a longest-common-subsequence (LCS) algorithm to compute line-by-line differences, showing added lines in green and removed lines in red — all in your browser, nothing uploaded.
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Text Diff FAQ
How does the text diff checker work?
Paste your original text in the left box and the changed version in the right box. The tool computes a line-by-line difference using a longest-common-subsequence (LCS) algorithm, then highlights added lines in green and removed lines in red.
Is the diff checker free?
Yes — completely free, no signup, no login, no limits.
Is my text private?
Yes. The entire diff is computed in your browser. Neither text is uploaded, logged, or tracked — important when comparing sensitive documents, contracts, or code.
Does it compare word-by-word or line-by-line?
Line-by-line. Each line is treated as a unit. If a single word changes within a line, the whole line shows as removed (old) + added (new). Line-level diffing is the standard approach used by Git and most diff tools.
Can I compare code?
Yes. The diff works on any text including source code, config files, JSON, CSV — anything line-based. Monospace font preserves alignment.
How big a document can it handle?
The LCS algorithm is O(n×m) in lines, so it comfortably handles documents of a few thousand lines. Extremely large files (tens of thousands of lines) may slow down since it runs entirely in the browser.