Which Unicode character can join multiple emoji into one displayed glyph?

The Zero-width joiner, or ZWJ, can join multiple emoji characters into one displayed emoji glyph. It is the invisible Unicode character U+200D, placed between visible emoji components in a defined sequence.

A familiar example is the family emoji, which can be constructed from person characters linked by ZWJ characters. Other sequences combine an object with a person or join symbols to produce professions, gestures, and gender-specific forms. The ZWJ itself has no visible width; its role is to tell a text renderer that the neighboring characters may be treated as a single grapheme-like emoji sequence.

The result is not guaranteed on every device. Unicode publishes recommended ZWJ sequences, but an older font or operating system may show the components separately, or display an unsupported-sequence fallback. That is why the same text can look like one pictograph on one platform and several emoji on another. A variation selector is different: it requests text or emoji presentation, while a zero-width space separates words without joining their appearance.