About diffvoid.com
diffvoid.com is a secure, private, browser-based text comparison tool. All processing happens locally in your browser-your text never leaves your device.
Key Features
- Privacy first: No server uploads, no tracking, no analytics. Everything stays in your browser.
- Line-aware diff: Uses sequence alignment so inserted or removed lines do not shift the whole comparison.
- Character-level diff: Within modified lines, shows exactly which characters differ.
- Invisible character detection: Highlights zero-width spaces, non-breaking spaces, and other hidden Unicode characters that can cause subtle bugs.
- Copy without invisible characters: When invisible characters are detected, copy buttons appear to copy clean text. Zero-width characters are removed completely, while special spaces (NBSP, En/Em space, etc.) are replaced with standard spaces to preserve word separation.
- Adjustable panels: Drag the center divider to adjust left/right panel widths. Double-click to reset to 50/50.
- Clear button: One-click to clear both panels and reset to default view.
- Dark mode: Toggle between light and dark themes with preference saved locally.
How It Works
The tool aligns lines using an LCS/heuristic strategy so matching blocks stay aligned even when lines are inserted or removed in the middle.
Within aligned modified lines, a character-level diff highlights exact differences.
Character-level processing switches automatically between two internal algorithms:
- DP (LCS matrix) for typical text sizes.
- Hirschberg (linear memory) for very large inputs.
Because comparison is fully browser-side, a safe practical limit is around 10,000 lines per side.
All computation happens client-side using JavaScript. There is no backend processing your text.
Detected Invisible Characters
- Zero-width space (U+200B)
- Zero-width non-joiner (U+200C)
- Zero-width joiner (U+200D)
- Non-breaking space (U+00A0)
- Hair space, thin space, en space, em space (U+200A, U+2009, U+2002, U+2003)
- Soft hyphen (U+00AD)
- BOM / zero-width no-break space (U+FEFF)
- And many more Unicode whitespace characters
How to Read the Diff
- Matching lines: No background highlight - text is identical.
- Modified lines: Red background with red characters showing exact differences.
- Added lines: Red background - appears only on the right side.
- Missing lines: Red background - appears only on the left side.
- Invisible characters: Shown as symbols like
|,[ZWSP], or red boxes for spaces in diffs.
Open Source
diffvoid.com is open source. You can inspect the code, verify the privacy claims, or contribute:
Contact
Created by Timo Heimonen
Email: timo.heimonen@proton.me