For the site, it doesn't matter. For someone who wants to build a new browser that supports EME, it does matter. There is no standard CDM API, so they must get

For the site, it doesn't matter. For someone who wants to build a new browser that supports EME, it does matter. There is no standard CDM API, so they must get copy open-source code (from Firefox or Chrome) or rely on documentation from a closed-sourced CDM. For Firefox, Mozilla has a plugin ABI called GMP (Gecko Media Plugin) similar to NPAPI. Unlike NPAPI, GMPs are not directly instantiated by web content and, AFAIK, the list of supported GMPs is hardcoded in Firefox. Cisco's OpenH264 codec and Adobe's Primetime CDM are GMPs. Google's Widevine CDM has its own API, so Firefox uses a Mozilla-written GMP that wraps Google's Widevine DLL or .so binary. https://wiki.mozilla.org/GeckoMediaPlugins https://wiki.mozilla.org/GeckoMediaPlugins