RotorLabMeasured from the service's own five-minute heartbeat and reported with the gaps left in. A day is green above 99.5% of its heartbeats, amber above 95%, red below. Grey days predate the record.
Self-reported honestly: a heartbeat cannot record its own outage while it is down, but it cannot invent uptime either — missing heartbeats are what you see here as amber and red. Machine-readable at /api/status.