M3G stands for “Metadata Management and distribution system for Multiple GNSS Networks”. GNSS station managers use M3G to upload, validate, and distribute their GNSS station metadata such as IGS-style site logs, information about local networks, data owner, DOIs, data license, etc...

M3G's primary goal is to collect rich metadata as recommended by the FAIR data principles. M3G's metadata of EPOS-GNSS stations are provided to the EPOS-GNSS Data Gateway and are also available through M3G's APIs and web portal.

M3G is maintained by the Royal Observatory of Belgium as a common service of EUREF and EPOS.