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, nominal data provision, licenses on the data, etc... M3G's metadata of EPOS GNSS stations are provided to the GNSS Data Gateway and are also available through M3G's APIs.