This presentation focuses on the role of reference implementations for the OGC standards process and gives an insight in the related OGC Compliance Program. OGC Standards are developed in the OGC Standards Program and follow rules and guidlines that have been set by the OGC's members. Before an OGC standard is adopted by the OGC membership, a public review period is required where non-members can also contribute. Increasingly, some standards working groups also decide to work more openly in the public (like the GeoPackage work group did) to be more inclusive. OGC interface standards also come with reference implementations. The OGC rules state that these have to be "free and publicly available for testing". Some well known OSGeo projects like GeoServer, MapServer, deegree and others are reference implementations of OGC standards. A Reference Implementation is a -> fully functional, licensed copy of a tested, branded software that has passed the test for an associated conformance class in a version of an Implementation Standard and that -> is free and publicly available for testing via a web service or download.