Custom emoji
Self-uploaded emoji that a workplace or community adds beyond the standard set — a load-bearing part of the culture in Slack and Discord. Inside jokes, colleagues' faces, and memes become clickable reactions.
Mechanic: anyone (or admins) uploads a small image and gives it a :name:; it can then be used in text and as a reaction. Culture: in many companies the custom emoji is an identity of its own — the boss's face as a reaction, a company mascot, "parrot" animations, status emoji (:loading:, :this:). They function as a shared language and a culture marker; a new employee learns the team partly through its emoji. Discord servers and Slack workspaces compete for the best ones. Distinct from stickers (their own messages) by being inline characters/reactions. An unexpectedly important tool for group cohesion online. Related to reaction emoji and slash commands.