Zero-Width Character Detector and Uses
Detect invisible zero-width characters in text — ZWJ, ZWNJ, ZWSP, and zero-width no-break space.
Published:
Tags: zero-width character detector, invisible characters Unicode, zero-width joiner detector
Zero-Width Character Detector and Uses Zero-width characters are invisible Unicode code points that affect text behavior without appearing on screen. They serve legitimate purposes in typography and complex script rendering — but they also appear in security attacks, plagiarism watermarking, and content filter evasion. --- The Zero-Width Character Family Six code points account for the vast majority of zero-width character appearances: | Code Point | Name | Abbreviation | Common Use | |------------|------|-------------|------------| | U+200B | Zero Width Space | ZWSP | Soft line-break opportunity | | U+200C | Zero Width Non-Joiner | ZWNJ | Prevent letter joining (Arabic, Devanagari) | | U+200D | Zero Width Joiner | ZWJ | Join emoji; force letter joining | | U+FEFF | Zero Width No-Break…
Frequently Asked Questions
What are zero-width characters?
Zero-width characters are Unicode code points that have no visible glyph and take up no horizontal space in rendered text. They influence line-breaking, ligature formation, and bidirectional text layout without appearing on screen. Common examples include Zero-Width Space (U+200B), Zero-Width Joiner (U+200D), and Zero-Width Non-Joiner (U+200C).
How do I detect zero-width characters in text?
Use a dedicated zero-width character detector that scans each code point against a list of invisible characters. A regex approach in JavaScript: /[-]/g. The detector should report the position and code point of each invisible character found, since they are impossible to spot visually.
What is a zero-width joiner (ZWJ)?
ZWJ (U+200D, Zero Width Joiner) is the Unicode character that requests adjacent emoji or letters be rendered as a single combined glyph. It is the core mechanism behind complex emoji: 👨💻 is MAN (U+1F468) + ZWJ + LAPTOP (U+1F4BB). It also controls ligature formation in Arabic and other scripts.
Are zero-width characters used maliciously?
Yes. Attackers embed zero-width characters in text to create watermarks that identify the recipient of a leaked document, to exfiltrate data by encoding bits in invisible character sequences, to bypass keyword filters, or to inject invisible instructions in AI prompts. Zero-width characters in source code can hide logic changes in what appears to be whitespace.
How do I remove zero-width characters?
In JavaScript: str.replace(/[-]/g, ''). In Python: import unicodedata; ''.join(c for c in s if unicodedata.category(c) != 'Cf'). Category 'Cf' covers format characters, which includes all zero-width characters. The zero-width detector tool provides one-click removal.
All articles · theproductguy.in