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Sending data as a message with a Slack incoming webhook URL

This technique uses this Action to post a message to a channel or direct message with incoming webhooks and a Slack app.

Incoming webhooks follow the same formatting patterns as other Slack messaging APIs. Posted messages can be as short as a single line of text, include additional interactivity with interactive components, or be formatted with Block Kit to build visual components.

Setup​

Gather a Slack incoming webhook URL:

  1. Create a Slack app for your workspace or use an existing app.
  2. Add the incoming-webhook bot scope under OAuth & Permissions page on app settings.
  3. Install the app to your workspace and select a channel to notify from the Install App page.
  4. Create additional webhooks from the Incoming Webhooks page.
  5. Add the generated incoming webhook URL as a repository secret called SLACK_WEBHOOK_URL.
  6. Add this Action as a step to your GitHub workflow and provide an input payload to send as a message.

The webhook URL will resemble something like so:

https://hooks.slack.com/services/T0123456789/B1001010101/7IsoQTrixdUtE971O1xQTm4T

Usage​

Add the collected webhook from above to a GitHub workflow and configure the step using mrkdwn formatting values for a message or Block Kit blocks:

- name: Post a message in a channel
  uses: slackapi/slack-github-action@v4.0.0
  with:
    webhook: ${{ secrets.SLACK_WEBHOOK_URL }}
    webhook-type: incoming-webhook
    payload: |
      text: "*GitHub Action build result*: ${{ job.status }}\n${{ github.event.pull_request.html_url || github.event.head_commit.url }}"
      blocks:
        - type: "section"
          text:
            type: "mrkdwn"
            text: "GitHub Action build result: ${{ job.status }}\n${{ github.event.pull_request.html_url || github.event.head_commit.url }}"

Expected outputs​

The technique, like all Slack Github Action techniques, outputs values that can be used as inputs in following steps of a GitHub workflow.

The following outputs are returned with each of the techniques:

OutputTypeDescription
timenumberThe Unix epoch time that the step completed.
okbooleanIf the request completed with success.
responsestringThe response from the request as stringified JSON.

Example workflows​

Post an inline text message

This workflow uses incoming webhooks to post a plain text message.

example-workflows/Technique_3_Slack_Incoming_Webhook/text.yml
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Post an inline block message

This workflow uses incoming webhooks to post a message with Block Kit.

example-workflows/Technique_3_Slack_Incoming_Webhook/blocks.yml
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Post blocks found in a file

This workflow uses file data when posting to an incoming webhook. It links to the GitHub Actions job in progress.

Payload file being sent

example-workflows/Technique_3_Slack_Incoming_Webhook/saved.data.json
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Workflow​

example-workflows/Technique_3_Slack_Incoming_Webhook/saved.gha.yml
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