Text Diff Checker
Paste original and changed text to find added, removed, and unchanged lines side by side — fully private, runs in your browser.
Original
Changed
Line-by-Line Diff
Uses an LCS (Longest Common Subsequence) algorithm to find the minimum set of additions and removals needed to transform the original into the changed text.
Fully Private
Your text is never uploaded to any server. All comparison runs locally in your browser.
Plain Text or Code
Works with any plain text — documents, configuration files, source code, markdown, CSV, or any line-based format.
How to compare two texts
- Paste your original text in the left panel and your changed text in the right panel.
- Click Compare.
- Green
+lines were added, red−lines were removed, and dim lines are unchanged. - Use the Swap button to reverse original and changed, or Clear to reset both panels.
Privacy — processed in your browser
Text comparison runs entirely in your browser using a built-in LCS (Longest Common Subsequence) algorithm. Your text is never sent to any server. This makes the tool safe for comparing drafts, source code, internal documents, or any sensitive content.
Frequently Asked Questions
Does this upload my text?
No. The diff algorithm runs entirely in your browser using JavaScript. Your text is never sent to any server, logged, or stored. You can safely compare confidential drafts, source code, contracts, and similar content.
What does a text diff checker do?
A diff checker compares two versions of text and shows exactly which lines were added, removed, or left unchanged. This is useful for tracking document revisions, reviewing code changes manually, comparing configuration files, or spotting differences between two copied versions of text.
Can I compare code or plain text?
Yes — this tool works with any plain text content: source code, Markdown, JSON, YAML, CSV, configuration files, prose documents, or anything line-based. For structured JSON comparison that ignores formatting and key order, try the JSON Diff Checker.
Does this show line-by-line differences?
Yes. The output is a unified-style diff showing every line from both texts, annotated with + (added), − (removed), or no symbol (unchanged). This gives a clear unified view of what changed between the two texts.
Is this private enough for drafts or sensitive text?
Yes. Because the comparison runs locally in your browser and no data is transmitted, this tool is as private as working in a text editor on your own device. No data is collected, no logs are kept, and no server processes your text.