Diffnote - Free Browser-Based Document Diff Tool

TL;DR

TL;DR: Diffnote is a free, privacy-first browser tool that compares TXT, PDF, DOCX, JSON, and Markdown files with side-by-side and unified diff views — all processing happens locally, files never leave your device.

Source and Accuracy Notes

⚠️ This section is MANDATORY. All links must be verified from actual source, not guessed.

• Project page: diffnote.net — verified by direct fetch, July 2026
• License: [not specified on the website; no visible LICENSE file on the main site]

What Is Diffnote?

Diffnote is a free, browser-based document comparison tool. You drop two files — or paste text directly — and Diffnote highlights every addition, deletion, and change across line, word, and character levels.

The entire comparison runs client-side in your browser. No files are uploaded to any server. This makes Diffnote particularly useful for:

• Developers comparing JSON configs or Markdown changelogs
• Writers reviewing revised drafts of TXT or DOCX files
• Security-conscious users who want zero data exposure

Setup Workflow

Step 1: Open the Tool

Navigate to diffnote.net. No account, no signup, no email prompt.

Step 2: Load Your Documents

You have three ways to provide documents:

1. Drag and drop — drag your original file onto the left pane, and your modified file onto the right pane
2. Browse — click the folder icon to open the native file picker
3. Paste text — paste raw text directly into either pane

Supported formats: TXT, PDF, DOCX, JSON, Markdown.

Step 3: Choose Comparison Mode

Click Compare Now. You can switch between:

• Side-by-side — original on the left, modified on the right
• Unified — changes shown inline in a single column

Within each layout, you can toggle the diff granularity:

• Line — highlights changed lines
• Word — highlights individual word changes
• Char — highlights individual character changes (most granular)

Step 4: Review and Export

Scroll through the highlighted diff. Green indicates additions, red indicates deletions. There is no export button documented on the site — you review changes visually and edit your files accordingly.

Deeper Analysis

Strengths

• Zero server contact — the site explicitly states “all processing happens locally in your browser”
• No signup wall — paste or drop immediately, zero friction
• Multiple format support — handles the most common plain-text and document formats
• Three diff granularities — line, word, and character levels cover all use cases
• Dark mode — the site ships with a theme switcher in the top-right corner

Limitations

• No PDF OCR — scanned PDFs are compared as binary blobs, not extracted text
• No diff export — you cannot download a .diff patch file or unified diff output
• No batch comparison — only two documents at a time
• No browser extension — not available as a native app or browser add-on

How It Compares to Alternatives

| Feature | Diffnote | VS Code Diff | WinMerge | GitHub Diff | |---|---|---|---|---| | No install | Yes | No | No | Yes | | PDF support | Yes | No | Yes | No | | Word/DOCX | Yes | No | Yes | No | | Privacy-first | Yes | Yes | Yes | No | | Word/Char diff | Yes | Partial | Yes | No |

Practical Evaluation Checklist

• Supports TXT, PDF, DOCX, JSON, Markdown
• Side-by-side and unified views
• Line, word, and character-level diff granularity
• Dark mode
• No signup required
• Entirely client-side — no server uploads
• Mobile-friendly (responsive layout)

Security Notes

Diffnote processes files entirely in your browser. The JavaScript that runs the comparison is loaded from diffnote.net but executes locally. There is no network request made when you compare two documents — the files remain in browser memory only.

However: the site uses Google Analytics (G-H43SW2XZ71). Page views and session data are tracked by Google, though not the document contents themselves.

FAQ

Q: Does Diffnote work offline? A: Once the page is loaded, the comparison engine runs entirely in the browser JavaScript runtime with no outbound requests. A service worker is not documented, so initial load requires an internet connection.

Q: Can I compare two different file types? A: Yes. You can compare a .txt file against a .json file, or a .md file against a .docx. Diffnote compares the text content of both.

Q: Is there a size limit? A: No explicit limit is documented on the site. Very large files may strain browser memory but should work within typical file sizes (under 10 MB per file).

Q: Can I use Diffnote programmatically? A: No API is available. Diffnote is a manual, web-based tool only.

Q: Is the source code open source? A: The site does not link to a source repository. The launch HN post (5 points) did not include a GitHub link.

Conclusion

Diffnote fills a specific niche: free, instant, privacy-respecting document comparison with support for both code-adjacent formats (JSON, Markdown, TXT) and office formats (PDF, DOCX). It requires no install, no account, and sends no data to servers.

For developers who need a quick diff without firing up VS Code or a terminal, or writers comparing two document versions without uploading to Google Docs, Diffnote is a clean, no-frills solution.

Try it: diffnote.net