Text Diff
Compare two texts side by side and highlight the differences.
About Text Diff
Spotting what changed between two versions of a document by eye is slow and error-prone. This free text diff tool lets you compare two texts online and see every difference highlighted instantly: paste the original on the left, the modified version on the right, and click Compare. Added lines are marked in green with a plus sign, removed lines in red with a minus sign, and unchanged lines stay neutral — the same familiar layout developers know from Git. Everything runs locally in your browser, so contracts, source code, and drafts are never uploaded anywhere.
The comparison uses a longest-common-subsequence algorithm — the same approach behind professional diff tools — so it finds the minimal set of changes rather than flagging everything after the first difference. Each line in the output carries its original and modified line numbers, and summary cards count exactly how many lines were added, removed, and unchanged. Writers use it to check edits between essay drafts, developers to review config file changes, and legal and business teams to find differences between contract versions. A one-click Swap button reverses the two sides, and Clear resets everything for the next comparison.
How to compare two texts online
- 1Paste the first version of your text into the Original pane on the left.
- 2Paste the second version into the Modified pane on the right. A live line count appears under each box.
- 3Click Compare to generate the diff. Use Swap to reverse the two sides, or Clear to empty both panes.
- 4Review the summary cards showing how many lines were added, removed, and unchanged.
- 5Scan the diff output — green lines with + were added, red lines with - were removed, and line numbers on both sides show exactly where each change sits.
Frequently asked questions
How does the comparison work?
The tool compares the two texts line by line using a longest-common-subsequence (LCS) algorithm — the same family of algorithms used by Git and professional diff tools. This finds the minimal set of added and removed lines instead of marking everything after the first change as different.
Is the comparison case- and whitespace-sensitive?
Yes. Lines must match exactly to be considered unchanged, so a difference in capitalization, a trailing space, or a changed indent will show as a removed line plus an added line. This makes the tool precise enough for source code and configuration files.
Is there a limit on how much text I can compare?
There is no fixed limit. Both panes accept arbitrarily long text, and since the comparison runs on your own device, the practical ceiling is your browser’s memory — typical documents and source files compare instantly.
Is my text uploaded to a server?
No. The entire comparison happens locally in your browser — nothing you paste ever leaves your device, and nothing is stored or logged. That makes it safe for comparing contracts, private drafts, and proprietary code.
Is this text compare tool free?
Yes — completely free, with no sign-up, no ads on your content, and no limits on how many comparisons you run.
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