ZeroWidthCharacters

Zero-width characters are invisible characters that do not occupy any horizontal space when rendered. Despite their invisibility, they are recognized by computers and can affect text processing, formatting, and even security. These characters are part of the Unicode standard and have specific code points.

Common examples of zero-width characters include the zero-width space (ZWSP), zero-width non-joiner (ZWNJ), zero-width joiner (ZWJ), and zero-width no-break space (ZWNP). The ZWSP is used to indicate a potential line break point without visually breaking the word. ZWNJ and ZWJ are used in complex script rendering, such as Arabic or Indic scripts, to control character joining and shaping. ZWNP prevents a line break at its position.

These characters can be intentionally inserted to manipulate text in various ways. For instance, they can be used to bypass content filters, as the characters are often ignored by simple text-matching algorithms. They can also be used for obfuscation, making text appear as one thing to humans while being interpreted differently by machines. Security vulnerabilities have been found where zero-width characters have been used to disguise malicious code or URLs.

Detecting and handling zero-width characters requires specific libraries or tools that are aware of their existence and purpose. Many text editors and word processors offer options to display or remove these invisible characters. Their use is generally discouraged in plain text communication unless there is a specific, well-understood purpose, such as in linguistic analysis or complex script typesetting.