Text Diff Checker
Compare two versions of any text and instantly see exactly what changed — additions in green, deletions in red.
How to Use the Text Diff Checker
- Paste Original Text — Paste your original or first version of text into the left input box.
- Paste Modified Text — Paste your updated or second version of text into the right input box.
- Click Compare Texts — The tool runs a line-by-line diff comparison instantly in your browser.
- Review the Differences — Green lines are additions in the modified text. Red lines are deletions from the original. Unchanged lines appear normally.
- Check the Summary — See the total count of added, removed, and unchanged lines in the chips above the diff output.
Key Features
Colour-Coded Diff
Green for additions, red for deletions, plain for unchanged — see every change at a glance without reading line by line.
Line Numbers
Line numbers in the output make it easy to reference exact locations in the original or modified text.
Change Summary
A quick summary shows total added lines, removed lines, and unchanged lines before the detailed output.
Works with Code
Compare code files, config files, HTML, JSON, CSV, and any other plain text format.
100% Private
All comparison happens locally in your browser. Your text never reaches any server.
Instant Results
No upload, no waiting. The diff output appears the moment you click Compare.
How the Diff Algorithm Works
Text diff checking is powered by the Longest Common Subsequence (LCS) algorithm — the same foundational approach used by version control systems like Git. The algorithm finds the longest sequence of lines that appears in both texts in the same order, then marks everything else as either added or deleted.
Here's a simplified example of how the comparison works:
Original: "The price is ₹500" Modified: "The price is ₹550"LCS: "The price is ₹" (common prefix) Result: - "The price is ₹500" [deleted] + "The price is ₹550" [added]
Line-by-line comparison is the most practical mode for documents, code, and configuration files. Each line is treated as a unit, so even a single character change marks the whole line as modified (shown as one deleted line and one added line).
The algorithm runs efficiently in your browser using a simplified Myers diff approach, handling texts up to 50,000 characters per box without any performance issues.
Practical Examples
Kartik deployed a config file update and needed to verify what actually changed versus the backup. He pasted both versions into the diff checker and instantly saw three changed lines and one new line — exactly what the deployment logs should have shown.
✔ Config changes verified in 10 secondsMeera sends articles to clients and receives revised versions back. Instead of reading both versions manually, she pastes them into the diff checker and sees exactly which sentences were changed, what was added, and what was cut — making approval far faster.
✔ Revision review time cut by 80%James received an updated contract version from a counterparty. Rather than reading 12 pages twice, he pasted both versions into the diff checker. The output immediately highlighted the two clauses that had been changed, saving significant review time.
✔ Contract changes spotted instantlyPreethi asked students to revise an essay based on feedback. She uses the diff checker to compare submitted revision against original draft — immediately seeing which suggestions were acted on and which weren't, without re-reading the entire essay.
✔ Revision tracking for 30+ studentsWhat Is a Text Diff Checker?
A text diff checker is a tool that compares two versions of a text and shows you exactly what changed — what was added, what was deleted, and what stayed the same. The name comes from "diff," the Unix command-line utility that has performed this function since the 1970s and remains essential in software development today.
Beyond code, the use case for text diff checking is much broader. Any situation where two versions of a document exist and you need to understand the differences quickly — contract revisions, article edits, translated versions, policy updates, product descriptions — is a valid use case for this tool.
Without a diff checker, comparing two texts means reading both in parallel and manually identifying differences — a slow, error-prone process that gets harder the longer the text is. A diff checker automates this entirely, presenting the differences visually in seconds regardless of document length.
Want to understand how diff algorithms work and where text comparison matters most?
Read our full guide: Text Diff Checking Explained — From Git to Document Review →Frequently Asked Questions
Is this tool free to use?
How are differences highlighted?
Does it compare line by line or word by word?
Can I use it to compare code?
Is there a character limit?
Is my text kept private?
What diff algorithm is used?
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