At the end of 2023, when Navionics® Boating decommissioned its online chart viewer, and began requiring an active subscription to access previously purchased charts, many sailors started looking for an alternative. Today, C-MAP is the only web app offering free worldwide coverage of nautical charts. There’s also a thriving ecosystem of free nautical charts available for download, click here if that’s what you’re looking for.
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C-MAP ONLINE chart viewer
C-MAP’s free Web Viewer and Mobile App are clear winners because they leveraging professional-grade marine cartography (owned by Navico). This makes it a trustworthy solution, even though the free version lacks advanced features like GPS navigation, route planning, weather overlays, and offline access.
Coverage extends worldwide with navigation aids, and regular updates reflecting official Notice to Mariners. Depth contours and soundings are clearly displayed, though resolution may vary by region.
A mention for i-Boating free chart viewer
Available both as a Web viewer and Mobile App, i-Boating’s free version serves as an introduction to their paid products. However, i-Boating takes a different approach by providing more basic cartography with less detailed features. Depth contours are shown at wider intervals, and small-scale features like rocks or shoals might not be as clearly marked. While US waters are well documented thanks to the open NOAA charts, international coverage can be patchy and may lack the detail needed for close-quarters navigation. Still, I’ve included i-Boating here as a backup as it remains a free worldwide coverage as of today.
OpenCPN for offline nautical charts
OpenCPN is a powerful open-source navigation software for desktop, offering free offline access to a variety of official government charts within the app.
Beyond basic chart display, OpenCPN supports route planning, GPS tracking, and integration with various navigation instruments. OpenCPN does require some initial setup to download and install appropriate charts, and in contrast to C-MAP the coverage is not global if you don’t own the charts. OpenCPN’s versatility lies in its ability to switch between any compatible chart format you can provide, including S-57, S-63, BSB/KAP, CM93, NV-Charts, and Navionics charts when properly formatted. However, users need to source these other charts separately, either by purchasing them from chart providers or downloading the free government-issued charts available within the app. A one-time-payment mobile app is also available, but only for Android at this time.
ActiveCaptain, Aqua Map, Argo, Marine Ways, and OpenSeaMap have also been evaluated among others, but were not included primarily due to their coverage limitations. If you know of another online chart viewer offering free worldwide coverage, please share it in the comments.