About DiffCheck
DiffCheck is a fast, free, client-side diff tool for text and code. No account. No limits. No data sent anywhere.
Why we built this
Diffchecker used to be the go-to free diff tool for developers and writers. As they've gradually moved core features behind paid plans, we wanted to offer a clean, modern alternative that stays permanently free. DiffCheck gives you the same side-by-side and inline views, character-level highlighting, and syntax support — with no strings attached.
Privacy-first by design
Every diff is computed locally in your browser using JavaScript. Your text is never transmitted to any server, never stored, and never logged. This makes DiffCheck safe to use with sensitive content: source code, contracts, configuration files, credentials, or any private document you need to compare.
- Zero network requests for diff computation
- No cookies or tracking beyond standard analytics
- No account or sign-up required — ever
- Works offline once the page is loaded
Features
Side-by-side & inline views
Toggle between a parallel two-column view and a unified single-column view. Side-by-side is the default on desktop; inline on mobile.
Character-level highlighting
Within each changed line, DiffCheck highlights the exact words and characters that differ — not just the whole line.
Syntax highlighting
Supports 15+ languages: JavaScript, TypeScript, Python, JSON, HTML, YAML, SQL, CSS, Go, Rust, Java, C/C++, Bash, Markdown, and plain text.
Statistics summary
A quick stats bar shows how many lines were added, removed, and unchanged — plus a one-click copy for the unified diff output.
Dark mode
Follows your system preference automatically. Click the toggle in the header to override.
Swap & clear
One-click swap to reverse original and modified. One-click clear to start fresh.
Open and free
DiffCheck is ad-supported to keep the lights on, but all features are free and unlimited. There are no paid tiers, no rate limits, and no paywalls.