Offline tide charts & alerts
Fast, dependable NOAA tide predictions for 1,200+ US coastal stations — computed right on your iPhone, so it works with no signal at the coast.
Questions, a bug, or a station you'd like added? Email us — we read every message.
Email supportIt helps to include your iPhone's iOS version and, if it's about a specific spot, the station name. We usually reply within a few days.
First, make sure notifications are enabled for Tidekeeper in iOS Settings → Notifications → Tidekeeper. Alerts are scheduled on-device and fire even when the app is closed and offline — but if notifications were ever declined, iOS won't deliver them until you turn them back on. Note that removing or unfavoriting a station also turns off its alerts.
Yes. Every prediction is computed on your device from official NOAA harmonic data bundled inside the app. There's no network request, no server, and no account — it works in a cove, on the water, or in airplane mode.
From NOAA CO-OPS published harmonic constants (public domain), referenced to Mean Lower Low Water (MLLW), the standard US chart datum. Predictions closely match NOAA's official tables for planning purposes.
1,200+ US reference (harmonic) tide stations across the coasts, Gulf, Alaska, Hawaii, and territories. Want one that's missing? Email us and we'll look at adding it.
Unlimited favorite stations, alerts on as many stations as you like, and the extended forecast — a single one-time purchase, no subscription. Already bought it? Use Settings → Restore Purchase on a new device.
No. Tidekeeper is for planning and recreation. Don't use it as your sole tool for navigation or life-safety decisions — consult official sources and local conditions.