Slack Block Kit

A UI framework for building rich, interactive app surfaces in Slack using stackable JSON components.

Block Kit streamlines Slack app development by replacing legacy attachments with a modular UI framework. Developers assemble layouts using 15+ distinct block types (such as section, input, and accessory) to build modals, home tabs, and complex message threads. It supports interactive elements like date pickers, multi-select menus, and radio buttons to drive user workflows directly within the client. By utilizing the Block Kit Builder for prototyping, teams can rapidly iterate on JSON payloads that ensure consistent rendering across desktop and mobile interfaces.

https://api.slack.com/block-kit