Slack Block Kit Builder
Compose Slack Block Kit payloads with sections, headers, dividers, buttons, and inputs - live rendered preview, reordering, and copy-paste JSON. Free and in-browser.
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What is Slack Block Kit Builder?
The Slack Block Kit Builder composes rich Slack message payloads visually: add sections, headers, dividers, buttons, and inputs, reorder them freely, watch a Slack-styled preview mirror your changes, and copy the finished JSON straight into a webhook or API call.
Key Benefits
- Structured Block Kit JSON without reading API docs
- Live preview mirrors layout and content as you type
- Reordering and deleting blocks without touching JSON
- Ready-to-paste payload for webhooks, APIs, and modals
Common Use Cases
- •Designing notification messages for CI and monitoring bots
- •Composing approval buttons and input modals for workflows
- •Prototyping rich announcements for team channels
- •Teaching teammates Block Kit structure with live examples
- •Iterating on bot replies without redeploying code
Build a Slack Message
- Add your first block: Pick a block type - section, header, divider, button, or input - and click Add block.
- Fill in the content: Each block exposes only its own fields: text for sections and headers, action IDs and URLs for buttons, labels and placeholders for inputs.
- Arrange the layout: Reorder blocks with the up and down arrows while the live preview mirrors exactly how Slack will render them.
- Copy into your app: Copy the JSON payload and paste it into a webhook call, the chat.postMessage API, or a modal definition.
Key Features
- Five block types: section, header, divider, button, and input
- Live Slack-styled preview that mirrors the payload exactly
- Reorder blocks up and down without touching JSON
- Buttons support action IDs and optional URLs
- Inputs render labels, placeholders, and action IDs
- One-click copy of the complete blocks payload