Alert channels have been growing steadily since v1.5: email in v1.5, generic webhooks in v1.7, Telegram from day one. This release adds Slack — the channel most teams already have open — using Slack's own Incoming Webhooks, which are free, don't need OAuth, and don't require App Store approval.
How it works
Create a Slack Incoming Webhook in your workspace (any channel, any app), copy the URL, and paste it into Settings → Notification channels. Checkmeup validates the URL against the `hooks.slack.com` pattern and sends a test message so you can confirm it's wired up correctly before saving. You can add multiple Slack webhooks — one per channel, team, or severity tier — each is its own channel record.
What the messages look like
Down alerts arrive as Block Kit messages: monitor name, type, failure reason, and timestamp — readable in Slack without opening Checkmeup. Recovery alerts add the downtime duration so the thread tells the whole story. Both use the same fire-and-forget delivery as the generic webhook channel: a non-2xx response (a removed or rotated webhook, for example) is logged in Settings, never blocks the check loop, and isn't retried automatically.
Channel selection per monitor
When creating or editing a monitor you choose which notification channels it uses — Slack webhooks, Telegram, email, or any mix. The per-incident alert cap introduced in v1.5 counts across all enabled channels together, so adding Slack to a monitor that already sends email doesn't double the alert volume for the same incident. Recovery alerts are always sent regardless of the cap.
Failure handling
Slack webhooks can be deleted or their URLs rotated. When a delivery fails (non-2xx or timeout), Checkmeup logs the error against the channel in Settings so you can spot a broken webhook and update it. The worker's check loop is never blocked waiting on a Slack response.
Follow along
Microsoft Teams alerts are next on the list, built on the same webhook delivery foundation. Releases land on this blog as they ship; the GitHub repo has the full commit history and architecture decision records for the notification channel model.
— Andrew