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qtVlm vs OpenCPN: catalog facts
qtVlm	OpenCPN
Screenshots	Screenshots
Best for: Cruising and racing sailors who plan routes around weather	Best for: Sailors who want a full chartplotter on a laptop or onboard computer
Free + paid options The GRIB viewer is free; mobile and tablet apps, chart packs and the GRIB service are paid.	Free Free and open source.
Windows, Android, iOS	Windows, macOS, Linux, Android
Weather routing with departure-time comparison Reads S57, S63, raster and MBTiles charts AIS and NMEA instrument support Iridium GO certified	Runs on Windows, macOS, Linux, Raspberry Pi and Android Plugin manager with a catalog of community plugins Designed for use at the helm while underway No cost for the software itself
Mobile versions and chart packs are paid Wide feature set takes time to learn	Desktop-style interface is less suited to phones than dedicated mobile apps Some chart sets must be obtained separately
Downloadable app	Downloadable app
Not open source	Open source
License not stated	License not stated
Not stated if an account is needed	No account needed
Not stated if it works offline	Offline features available
Official website Full listing and sources Sources for qtVlm meltemus.com apps.apple.com/us/app/qtvlm/id999110023 Catalog checked September 24, 2026	Official website Full listing and sources Sources for OpenCPN opencpn.org play.google.com/store/apps/details Catalog checked September 23, 2026

“Not stated” means we have not confirmed it. Features can vary by device and plan.

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