> ## Documentation Index
> Fetch the complete documentation index at: https://docs.suprsend.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Slack

> Design Slack notification templates using the Text editor for simple messages or the JSONNET editor for rich Block Kit layouts.

The Slack editor supports two modes: a **Text** editor for simple messages, and a **JSONNET** editor for rich [Block Kit](https://api.slack.com/block-kit) layouts with buttons, images, and structured sections.

<Frame caption="Slack editor with JSONNET and live preview">
  <img src="https://mintcdn.com/suprsend/sGhtraHJZNmyh1Op/images/docs/templates-editor-slack.png?fit=max&auto=format&n=sGhtraHJZNmyh1Op&q=85&s=9cea93df1c60ed76d2875e5e29621f50" width="1024" height="561" data-path="images/docs/templates-editor-slack.png" />
</Frame>

<Note>
  To send Slack notifications, you need a Slack vendor integrated with SuprSend. See [Slack vendor integration](/docs/slack) for setup.
</Note>

## Slack fields

**Text mode** — a single text field. Supports [Handlebars](/docs/handlebars-helpers) variables (`{{variable_name}}`). Use triple braces `{{{url}}}` for URLs with special characters.

**JSONNET mode** — a code editor that outputs [Slack Block Kit](https://api.slack.com/block-kit) JSON. Variables use `data.key` syntax (not Handlebars). Design visually in the [Block Kit Builder](https://app.slack.com/block-kit-builder/) first, then adapt the JSON into JSONNET. See the full [JSONNET reference](/docs/jsonnet-templates) for syntax, examples, and debugging.

<Tip>
  **AI prompt — convert text to Block Kit:** *"Convert this Slack notification into Block Kit JSON: \[paste message]. Variables: \[list]. Return valid JSON I can adapt into JSONNET for SuprSend (replacing values with data.key)."*
</Tip>

<Tip>
  **AI prompt — debug JSONNET:** *"Fix this JSONNET error from the SuprSend Slack editor. Error: \[paste error]. Code: \[paste JSONNET]. Variables are accessed as data.key or data\['\$special\_key']."*
</Tip>

<Info>
  You can switch between Text and JSONNET at any time. Content is saved independently for each mode.
</Info>

## Adding dynamic content

**In Text mode** — type `{{` for auto-suggestions. Standard Handlebars syntax:

* `{{order_id}}` — top-level variable
* `{{order.address.city}}` — nested variable
* `{{{tracking_url}}}` — URL (avoid escaping)
* `{{$recipient.name}}` — recipient property
* `{{$brand.brand_name}}` — tenant property

**In JSONNET mode** — variables use `data.key` syntax. See [JSONNET variable reference](/docs/jsonnet-templates#variable-syntax) for the full table.

For conditionals, loops, and helpers in Text mode, see [Handlebars Helpers](/docs/handlebars-helpers).

<Warning>
  If a variable cannot be rendered at send time (missing or mismatched data), SuprSend discards the Slack notification for that user. Other channels in the same template group are still sent.
</Warning>

## Preview and test

**Text mode** — the right panel shows a Slack message preview. It does not update automatically — **refresh the page** to see the latest changes.

**JSONNET mode** — preview is not available in the editor. Click **View on Slack Builder** to render and validate your Block Kit output in Slack's [Block Kit Builder](https://app.slack.com/block-kit-builder/).

Click **Test** in the top-right corner to send a real Slack message. This uses the **live version** — commit your changes before testing. See [Testing a Template](/docs/templates#test) for the full guide.

## Commit

Click **Commit** in the top bar to publish the current draft as a new live version. Add an optional description for versioning.

## Common patterns

<AccordionGroup>
  <Accordion title="Thread-aware notifications">
    Slack automatically threads messages sent to the same channel with the same `thread_ts`. Pass a consistent `thread_ts` in your trigger payload to keep related messages threaded.
  </Accordion>

  <Accordion title="Mentioning users">
    Use `<@SLACK_USER_ID>` to @mention a user. Pass the ID as a variable: `<@{{assignee_slack_id}}>`.
  </Accordion>

  <Accordion title="Linking to resources">
    Slack uses `<URL|display text>` syntax. In JSONNET: `"*<" + data.url + "|" + data.title + ">*"`.
  </Accordion>

  <Accordion title="Emoji">
    Use `:emoji_name:` syntax (e.g., `:white_check_mark:`, `:warning:`).
  </Accordion>
</AccordionGroup>

## Frequently asked questions

<AccordionGroup>
  <Accordion title="Text or JSONNET — which should I use?">
    Start with Text for simple alerts and status updates. Switch to JSONNET when you need buttons, images, structured layouts, or batched event lists.
  </Accordion>

  <Accordion title="How do I validate my Block Kit JSON?">
    Click **View on Slack Builder** in the JSONNET editor. Slack silently drops invalid blocks instead of showing errors — always validate before committing.
  </Accordion>

  <Accordion title="What's the message length limit?">
    Slack truncates messages over 4000 characters. For batched notifications with many items, show the top 5-10 and add a "View all" button.
  </Accordion>

  <Accordion title="What formatting does Slack support?">
    Slack uses `mrkdwn`, not standard Markdown. Bold: `*text*`, italic: `_text_`, strikethrough: `~text~`, code: triple backticks.
  </Accordion>

  <Accordion title="What happens if a variable is missing at send time?">
    SuprSend discards the Slack notification for that user. Other channels in the same template group are still sent.
  </Accordion>
</AccordionGroup>