Question 1

How does the text diff work?

Accepted Answer

The tool splits both texts into lines and computes a longest-common-subsequence (LCS) between them. Lines that appear in both texts in the same order are marked unchanged; lines present only in the original are marked removed (red); lines present only in the changed text are marked added (green). This is the same core algorithm used by tools like git diff.

Question 2

Does it compare line by line or word by word?

Accepted Answer

The comparison is line-level: each line is treated as a unit and is either matched, added, or removed. This keeps results clear and predictable for prose, code, configuration files, and lists. A change anywhere within a line marks that whole line as removed and its replacement as added.

Question 3

Is my text private? Is anything uploaded?

Accepted Answer

Nothing is uploaded. All comparison logic runs entirely in your browser using JavaScript, so your text never leaves your device. This makes the tool safe for comparing sensitive content such as contracts, private documents, or code containing secrets.

Question 4

What do the colors mean?

Accepted Answer

Green lines with a plus sign were added in the changed text. Red lines with a minus sign were removed from the original. Neutral, un-highlighted lines are unchanged and appear in both texts. Each row also shows the corresponding line number in the original and changed text.

Question 5

Can I compare source code or JSON?

Accepted Answer

Yes. The tool works with any plain text, including source code, JSON, CSV, Markdown, and log files. Whitespace and indentation are significant, so two lines that differ only in leading spaces are treated as different lines — useful for spotting formatting changes.

Text Diff