Twitter’s original emoji image set, released in 2014, was called Twemoji.
The name combines “Twitter” with “emoji.” Twitter developed the set so its service could display a consistent visual interpretation of emoji across platforms and devices. In 2018, Twitter released Twemoji artwork under a permissive Creative Commons license, helping developers and websites use the designs outside Twitter.
Twemoji is an artwork set, not a separate encoding standard. The Unicode Standard defines the characters and sequences, while Twemoji supplies one way to draw many of them. Other major families include Google’s Noto Color Emoji, Microsoft’s Fluent Emoji, and Apple’s platform-specific designs.
Because artwork differs by vendor, the same Unicode emoji can have noticeably different expressions, colors, or object shapes. Twemoji’s simple, outlined style became particularly recognizable on websites and in open-source projects.