About LocalDiff.dev
Your data never leaves your browser.
LocalDiff.dev was built for developers, writers, and teams who need fast, private text and code comparison — without trusting a third-party server with their content.
100% Local Processing
Our Mission
Every other online diff tool sends your text to a server. We think that's wrong. Code can contain secrets. Documents can contain confidential data. You shouldn't have to trust a stranger's server to compare two files.
LocalDiff.dev processes everything in your browser using native JavaScript. Nothing is uploaded. Nothing is stored. Close the tab and it's gone.
Core Principles
🔒
Privacy by default All diffing happens in your browser. The only time network traffic occurs is when you use the AI merge feature, which sends only the conflicting text — not your full documents — to Google Gemini via an anonymized proxy.
⚡
Fast and free No sign-up, no account, no waiting. Open the page and start comparing immediately. Free tier supports 10 comparisons per day.
🎨
Developer-grade tooling Syntax highlighting for 20+ languages, word-level diff granularity, split and unified views, drag-and-drop file upload, and URL content fetching.
🤖
AI-assisted merging Powered by Google Gemini 2.0 Flash. When you have conflicting changes, AI smart merge suggests the best resolution — you always stay in control.
Tech Stack
Frontend
React 19 + TypeScript
AI
Google Gemini 2.0 Flash
Backend
Express.js (proxy only)
Syntax
Prism.js (20+ languages)
Diff Engine
diff.js (Myers algorithm)
Sustainability
LocalDiff.dev is free to use and supported by non-intrusive advertising (Google AdSense) and affiliate links to developer tools we actually use and recommend. Ads are clearly labeled and never placed over the core diff interface.
If you find LocalDiff.dev useful for your work, consider supporting us by exploring our recommended tools or sharing the site with colleagues.