How to Compare Text & Code Privately Online
LocalDiff.dev is a free, privacy-first text and code comparison tool that runs entirely in your browser. Unlike other online diff tools, your data never leaves your machine — there are no server uploads, no data logging, and no privacy risks.
Why Use LocalDiff.dev?
100% Private
All diff processing happens in your browser. No text is ever uploaded to any server. Perfect for sensitive code, contracts, or confidential data.
Merge Change by Change
Keep the original or accept the modified version of each change, then copy or download the merged result.
Word-Level Diffs
See exactly which words changed within each line, not just which lines are different. With syntax highlighting for popular languages.
Zero Setup
No downloads, no installation, no sign-up. Just open your browser and start comparing. Works on desktop and mobile.
Step-by-Step Guide
1. Input Your Content
You have three ways to input content into each panel:
- Paste: Copy-paste text directly into the "Original" (left) and "Modified" (right) text areas
- Open or drop files: Click the upload button or drag a file onto a panel. Drop two files at once to fill both panels. Files are read locally and never uploaded.
- URL Fetch: Enter a URL and click Fetch to load remote content
2. Compare
Click the Compare Sources button at the bottom of the screen. You'll see your differences highlighted in a visual diff view.
3. Choose Your View
- Split View: Side-by-side comparison with the original on the left and modified on the right
- Unified View: Traditional unified diff format showing all changes in a single column
4. Merge Changes
Hover over any changed block to see merge actions. You can:
- Keep the original version
- Accept the modified version
- Accept or keep removals, and accept or reject additions
5. Export Results
Download the merged result as a text file, or copy it to your clipboard.
Supported File Types
LocalDiff.dev works with any text-based content including:
- Source code: JavaScript, TypeScript, Python, Go, Rust, Java, C/C++
- Configuration: JSON, YAML, XML, TOML, INI, .env
- Documentation: Markdown, plain text, HTML, CSS
- Data: CSV, SQL, shell scripts
Frequently Asked Questions
- Is my data safe?
- Yes. All diff comparisons happen locally in your browser. Your data is never uploaded to any server.
- Do I need to create an account?
- No. LocalDiff.dev works without any sign-up or login.
- Is there a file size limit?
- Local text files and content fetched from a URL can each be up to 50 MB per panel. There is no limit on the number of comparisons.
- Can I compare binary files like images or PDFs?
- Currently, LocalDiff.dev supports text-based files only. Binary file comparison is on our roadmap.
- Does it work offline?
- Core diff features work without an internet connection once the page has loaded. Only URL fetching needs connectivity.