GoAlert
6.1#18 in it alerting softwareFree planFree planWebAPISelf-hosted
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GoAlert suits teams that need to route on-call alerts through schedules and escalation policies and can host the software themselves. It is also relevant to teams with a PostgreSQL instance and a need for multiple alert sources and notification channels.
PagerDuty suits teams responsible for incident response, including developers, reliability engineers, customer success, and security teams. Its mobile app may be useful to responders who need incident context and schedule controls on iOS or Android.