Tideline: Offline Tide Charts

Tide predictions for every NOAA station, computed on your phone. Tideline makes no network request at any point after you install it.

WORKS WHERE YOUR SIGNAL DOES NOT

Most tide apps ask the internet. Tideline does the astronomy itself, from harmonic constants published by NOAA and bundled with the app. Down a canyon, offshore, on a beach with no bars, in airplane mode — it just works.

WHAT YOU GET

• 3,493 NOAA tide stations: 1,251 reference stations and 2,242 subordinate stations
• The full tide curve for any day, not just a table of times
• High and low water with heights above mean lower low water
• Where the water is right now, and whether it is rising or falling
• Times shown in the station's own local time, daylight saving handled correctly, computed offline
• Find the stations nearest you, or search by name or state

BUILT TO BE RIGHT

Tideline uses the harmonic method, the same one NOAA's own published tables come from. Predictions are checked against those tables: across a month, most stations agree to within a few hundredths of a foot, and the largest tide in the country agrees to about one percent of its 35-foot range.

Predictions are astronomical. They do not include weather — wind and barometric pressure routinely move real water by a foot or more, and by much more in a storm. Do not use any tide prediction as your only source for navigation.

NO ADS, NO SUBSCRIPTION, NO DATA COLLECTION

Free: every station, the full curve, seven days ahead, two saved stations. One payment lifts the station limit and extends predictions to a full year. It never expires.

There is no advertising, no subscription, no account and no analytics. Tideline collects nothing. If you grant location access it is used only to sort the station list by distance, and it is never stored or sent anywhere.

SOURCE OF THE DATA

Every number in Tideline originates with the NOAA Center for Operational Oceanographic Products and Services (CO-OPS), a US government agency, published at https://tidesandcurrents.noaa.gov

Harmonic constants, datums and prediction offsets come from there. Inside the app, every station screen links to that station's own official NOAA page, and Settings links to the NOAA sources directly.

Tideline computes predictions from NOAA's published constants and offsets. It does not redistribute NOAA's own predictions, and it is neither affiliated with nor endorsed by NOAA or any government agency.