The starting version
8 lines · 122 chars
Diff Checker
Free Online Diff Checker
A diff checker is an online tool that compares two text blocks, code, or JSON documents and highlights every line that was added, removed, or changed. Paste an original on the left and the new version on the right - the comparison runs instantly in your browser.
Side-by-side and unified views, line numbers, word-level highlights on partially-matched lines, and JSON-aware comparison. Nothing is uploaded - your text never leaves the page.
The new version to compare
6 lines · 115 chars
| # | Original | # | Changed |
|---|---|---|---|
| 1 | ·function greet(name) { | 1 | ·function greet(name = "friend") { |
| 2 | · if (!name) { | 2 | · return `Hello, ${name}!`; |
| 3 | - return "Hello, friend!"; | · | |
| 4 | - } | · | |
| 5 | - return "Hello, " + name + "!"; | · | |
| 6 | } | 3 | } |
| 7 | 4 | ||
| 8 | ·greet("world"); | 5 | ·console.log(greet("world")); |
| · | 6 | +console.log(greet()); |
How to use this diff checker
1
Paste your original text
Drop the original version of your text, code, or JSON into the left input box. Anything from a single line to thousands of lines is supported.
2
Paste the changed text
Drop the new version into the right input box. The diff updates live as you type, with no button to click.
3
Review the highlighted differences
Added lines appear in green, removed lines in red, and partially-changed lines show word-level highlights. Toggle side-by-side or unified view, copy the diff as Markdown, or swap sides with one click.
When to use a diff checker
Reviewing code changes
Spot-check what changed in a refactor or pull-request snippet without leaving your browser. Word-level highlights make small renames and condition tweaks easy to read.
Comparing JSON payloads
Toggle JSON pretty-print to normalize indentation and key order so structural changes between two API responses or fixtures are obvious instead of hidden under formatting noise.
Editing drafts
Paste an old and a new version of an article, contract, or marketing copy to see exactly which sentences moved or got rewritten - no track-changes needed.
Auditing config files
Compare two YAML or env files side-by-side before deploying so the exact set of intentional changes is verified line by line.
Frequently Asked Questions
What is a diff checker?
A diff checker is an online tool that compares two pieces of text, code, or JSON and highlights every line that was added, removed, or changed. It helps developers review edits, writers compare drafts, and ops teams audit configuration changes without needing a full version control system.
Is this diff tool free?
Yes. The NitroClaw diff checker is 100% free with no signup, no rate limits, no watermarks, and no file size limits beyond what your browser can handle. Run as many comparisons as you need.
Does my text leave my browser?
No. All diffing happens entirely in your browser using JavaScript. Your text is never uploaded to a server, logged, or stored. The tool also works offline once the page has loaded, which makes it safe for proprietary code, contracts, or sensitive content.
Can I diff JSON or code?
Yes. Paste any code, configuration file, or JSON document on each side and the diff is computed line by line. Turn on the 'Pretty-print as JSON' toggle to normalize both inputs with consistent indentation before diffing, which makes structural changes much easier to spot.
How does word-level highlighting work?
When two lines partially match, the tool runs a second word-level diff inside that line so the unchanged words stay neutral while only the added or removed words light up. This makes typo fixes, renamed variables, and small wording tweaks much easier to read than a plain line diff.