Slack Reactions API

Slack's Reactions API lets apps programmatically manage emoji reactions on messages and files, making it easy to capture lightweight feedback like approvals, acknowledgments, or votes. Through Web API methods (reactions.add, reactions.remove, reactions.get, reactions.list) and the Events API (reaction_added and reaction_removed), apps can add or delete reactions, read which reactions are on an item, and monitor reaction activity in real time. It works with messages (including threads), files, and file comments in channels, DMs, and group DMs where the app has access. Responses include reaction names, counts, and user IDs, and support both standard and custom emoji. Proper scopes (reactions:read and reactions:write, plus relevant conversation/file scopes) and channel visibility rules apply, rate limits are enforced, and each user can apply at most one instance of a given emoji per item.