Great question — in Prefect 2 there are two similarly named blocks that serve different purposes: - Slack Webhook (core) - Where it lives: Prefect core (

prefect.blocks.notifications.SlackWebhook

) - Install: Included with Prefect (no extra package) - Best for: Simple notifications from Prefect Automations/Notifications (UI-driven alerts) - Capabilities: Plain-text messages via a Slack Incoming Webhook URL - Docs: https://docs.prefect.io/api-ref/prefect/blocks/notifications/#prefect.blocks.notifications.SlackWebhook - Source: https://github.com/PrefectHQ/prefect/blob/2.x/src/prefect/blocks/notifications.py - Slack Incoming Webhook (prefect-slack collection) - Where it lives:

prefect-slack

integration (

prefect_slack.credentials.SlackWebhook

) - Install:

pip install prefect-slack

, then register blocks once:

prefect block register -m prefect_slack

- Best for: Sending messages from flows/tasks with richer formatting - Capabilities: Supports Slack attachments and Block Kit blocks, async-friendly helpers - Docs: https://docs.prefect.io/integrations/prefect-slack/credentials/#prefect_slack.credentials.SlackWebhook - Source: https://github.com/PrefectHQ/prefect/blob/2.x/src/integrations/prefect-slack/prefect_slack/credentials.py - Message helpers: https://github.com/PrefectHQ/prefect/blob/2.x/src/integrations/prefect-slack/prefect_slack/messages.py Which one should you use? - If you’re wiring up Prefect Cloud Automations/Notifications to Slack: use Slack Webhook (core). - If you want to send Slack messages from inside your flows/tasks (especially with attachments/blocks): use Slack Incoming Webhook (prefect-slack). Both blocks take the same kind of Slack Incoming Webhook URL; the difference is primarily where/how you use them and the richness of messages you want to send. If you instead need to use the Slack Web API with a bot token (e.g., post in threads, DM users), look at

prefect_slack.SlackCredentials

and related tasks: https://docs.prefect.io/integrations/prefect-slack/credentials/ Quick examples - Core block in an Automation (UI-driven) — configure the “Slack Webhook” block in the UI and select it in your Notification. - In-flow message with prefect-slack:

from prefect_slack import SlackWebhook
  from prefect_slack.messages import send_incoming_webhook_message

  webhook = SlackWebhook.load("my-slack-incoming-webhook")
  await send_incoming_webhook_message(
      slack_webhook=webhook,
      text="Flow finished ✅",
      slack_blocks=[{"type": "section", "text": {"type": "mrkdwn", "text": "*Success!*"}}],
  )

If you can share whether you’re setting up Cloud Automations or sending messages from inside a flow, I can recommend the exact setup (and code) to use.