Diff Checker
Compare two versions of text, line by line or word by word. Nothing you paste ever leaves this tab.
0 characters
Nothing you type here is sent anywhere.
0 characters
Nothing you type here is sent anywhere.
What this tool does
Diff Checker compares two blocks of text and highlights exactly what changed between them — additions, removals, and everything left untouched — either line by line or word by word. It's built for the ordinary need to see what actually changed between two versions of something: a config file, a paragraph of copy, a log snippet, an API response before and after a fix.
Paste the original into Before and the updated version into After, and the comparison appears automatically as you type.
How to use it
Paste the two versions into Before and After. Choose Lines to compare whole lines at a time (best for code, config, and structured text) or Words to compare word by word (best for prose, where a single word change shouldn't highlight the whole paragraph). The result highlights additions and removals directly, and updates automatically as you edit either side.
Copy the plain-text diff or download it. Clear both sides any time to start over. For very large inputs, live comparison pauses automatically and a button lets you run it on demand instead.
Why nothing leaves your device
The two things people diff most often are exactly the kind of content that shouldn't go anywhere near a server they don't control: a config file with credentials in it, a before/after of a customer record, an internal document that hasn't shipped yet. A server-backed diff tool means both versions of that content cross the network, twice, before you even see the result.
This comparison runs entirely with code already loaded in your browser tab — nothing is uploaded, and nothing about either version is kept once you leave the page. Check your network tab while using it and you'll see no request carrying anything you pasted.
What this does well — and what it doesn't
This handles text of essentially any size your browser can hold in memory, correctly identifies additions, removals, and unchanged content at both line and word granularity, and produces a clean, copyable plain-text diff alongside the visual highlight.
It doesn't diff files directly (PDF, Word documents, images) — only plain text you paste in. And on very large inputs (roughly 200,000 characters combined), live updating pauses to avoid freezing the tab; a manual button runs the comparison on demand instead, so it stays usable rather than getting stuck computing a diff on every keystroke.