Tidekeeper: Tides & Alerts
Luke Bradford
Tidekeeper gives you fast, dependable tide predictions for 1,200+ US coastal stations — and it works completely offline. Tide heights are computed right on your iPhone from official NOAA harmonic data, so you get the full curve and the next high and low even with no signal at the coast. Built around the things other tide apps get wrong: FAVORITES, FRONT AND CENTER Pin the spots you actually care about — your home break, the boat ramp, the fishing flat — and see all of them at a glance with the current height, whether the tide is rising or falling, and the next high/low with a live countdown. ALERTS THAT ACTUALLY FIRE Set high- and/or low-tide notifications and choose how far ahead to be warned (at the tide, or 15–120 minutes before). Because tides are predictable, Tidekeeper schedules them with the system — so they arrive on time even when the app is closed and your phone is offline. TRULY OFFLINE Everything is on-device: no network call, no backend, no API keys. Predictions keep working in a cove, on the water, or in airplane mode. A CLEAN, READABLE CHART See the day's tide curve with every high and low marked and a "now" line, plus a simple high/low table. Times are shown in the station's local time. YOUR PREFERENCES STICK Choose feet or meters and 12- or 24-hour time. Set it once; it stays that way. NO ACCOUNT. NO ADS. NO TRACKING. Tidekeeper doesn't ask you to sign in, doesn't show ads, and doesn't collect your data. ABOUT THE DATA Predictions are derived from NOAA CO-OPS published harmonic constants (public domain) and are referenced to Mean Lower Low Water (MLLW), the standard chart datum. They match NOAA's official predictions closely for planning purposes. NOT FOR NAVIGATION Tidekeeper is for planning and recreation. Do not use it as your sole tool for navigation or life-safety decisions; consult official sources and local conditions. TIDEKEEPER PRO Tidekeeper is free to use for your first favorites and their alerts. Upgrade to Pro for unlimited favorite stations, alerts on as many stations as you like, and the extended forecast — a single one-time purchase, no subscription required. Questions or a station you'd like added? We'd love to hear from you.