M3G, which stands for "Metadata Management and Distribution System for Multiple GNSS Networks", is developed and maintained by the GNSS team at the Royal Observatory of Belgium.
M3G consists of a web portal and an application programming interface (API), and provides free online access to validated and standardized GNSS station metadata including IGS-style site log files as well as information about local networks, DOIs, station pictures, etc.
Registered agencies can upload, validate, and distribute GNSS station metadata via the M3G portal.
M3G is free to use and is developed in alignment with FAIR data principles.