Slack Block Kit

Expert guide for building Slack UIs with Block Kit.

Overview

Block Kit is Slack's UI framework for creating rich, interactive messages, modals, and Home tabs. It uses a JSON-based structure with three main components:

• Blocks: Layout containers (Section, Actions, Input, Header, etc.)
• Elements: Interactive components (Buttons, Selects, Date pickers)
• Composition Objects: Text, options, and confirmations

Surfaces

Block Kit works on three surfaces: