In the space of a decade emoji have gone from being unavailable outside of Japan to active use by over 90% of the world’s online population. Their sudden rise in use is often attributed to the way they allow users to convey in writing what is usually done with tone of voice and body language in face-to-face interaction, but the specific implementation of this general claim has been under-explored. In this talk we look at the functional parallels between emoji and co-speech gestures. In addition to the obvious similarities between certain emoji and certain gestures (e.g., winking, thumbs up), gestures are commonly grouped into subcategories according to how codified their meaning is and how much they are dependent on surrounding speech. We look at how emoji fill the same set of functions, and argue that emoji give writing the same multimodality as speech and sign. We also bring in the bigger picture of why linguists should care about informal writing, and why the internet is an important place to study it.