SailorsLog — A Digital Logbook for the Modern Cruiser
On our recent winter sailing trip in Friesland, I finished building SailorsLog — a native iOS logbook app for sailors. It is now live on the App Store.
The idea came from my wish to make the voyages of Coelacanth available for sharing. I wanted something that worked without internet, handled photos intelligently on a satellite connection, and kept a proper record of the passage: departure and arrival ports, weather, crew, engine hours, distance. And store all that in a beautiful layout.
More features are GPX import from the chartplotter to overlay the route on a map, automatic GPS coordinate extraction from photo EXIF data, and a postcard generator for sharing a passage summary.
The app is built around an offline-first principle. Everything is stored locally the moment you type it — no internet required. When connectivity returns, it syncs to iCloud via CloudKit. Text goes first (minimal data), while photos and GPX tracks wait for Wi-Fi or until you explicitly ask for them. Useful when a gigabyte of satellite data costs what a marina berth does.
Multi-device sync was the hardest part to get right. The app uses field-level conflict resolution: if you edit the wind description on the iPad and the departure time on the iPhone while both are offline, both changes survive the merge. A naive last-write-wins approach would have silently dropped one of them.
Sebastian designed the app icon and never tired to do another betatest run. He also contributed photos for the app screenshots.
The app runs on iPhone, iPad, and Mac Catalyst. More at sailorslog.io or directly on the App Store.