Uptime alerts in Slack

Setting it up

1. In StatOSS, open the page's settings, Alerts, choose Slack under "Add a destination" and press Connect Slack. Pick the channel in Slack and allow it; you come back with the channel ticked for the page.
2. Or, in Slack, create an incoming webhook for the channel (Slack calls it an app with Incoming Webhooks turned on), copy the URL and paste it into the Slack webhook URL field instead. Save.
3. Press "Send a test alert". It tries every saved channel and says which ones took it, so a wrong URL shows up now rather than during an outage.

Slack is on Hobby ($4 a month) and Pro. Email alerts are on every plan, Free included. The pricing page has the rest.

What the message says

The page and monitor names, the URL, what failed (a timeout, a connection error, a status code, a missing keyword), the time, and on recovery how long the outage lasted. A link goes to the public page, where the strip shows the failed checks in context. One channel can take alerts from several pages, since each message names its page.

When an alert goes out

One alert per change of state: when a monitor goes down, when it turns slow, and when it is back, with the time, the reason, and how long it was out. A monitor counts as down after two failed checks in a row, each confirmed by a second server on another network; a single failed check sends nothing. A repeat interval sends a "still down" notice every so many minutes while an outage lasts, and nothing is sent during a maintenance window. Every kind of monitor alerts the same way: a website, an API, a port, a certificate, a cron job.