Unicode is the international character-encoding standard maintained by the Unicode Consortium. It assigns every character a unique number called a code point, written in the form U+0041 for the letter A, and that number stays the same on every platform, program, device and language.

The problem it solved was a practical one. Earlier encodings each covered a limited character repertoire, so the same byte value meant one character in one encoding and a different character in another. Text moved between systems arrived corrupted, and no single document could reliably mix scripts.

Unicode replaced that patchwork with one universal set covering Latin, Devanagari, Arabic, Chinese, Cyrillic and many more, along with punctuation, mathematical symbols and emoji. Its code points are stored using encoding forms such as UTF-8, UTF-16 and UTF-32, of which UTF-8 dominates the web. Support for Indian scripts is the reason a Marathi or Hindi page displays identically across devices.

Multicode, Hypercode and Metacode are not encoding standards; none of them names a recognised character-encoding system.

Hence the standard is Unicode.