Record the complete question
The Media Capabilities API asks about a described media configuration rather than an informal codec name. Keep the queried type, content type, dimensions, bitrate and frame rate with the result where applicable. If the question described a modest 1080p stream, its answer should not be transferred to an unrelated high-bitrate 4K stream. A partial screenshot of a true value omits information needed to interpret it.
Distinguish the returned properties
The W3C draft defines supported, smooth and powerEfficient fields. These address different aspects of the configuration, so avoid collapsing them into a single guaranteed-compatible badge. A developer should handle an unsupported or invalid configuration deliberately and retain the relevant browser and operating-system versions. The document reviewed here is a Working Draft, not proof that every feature or implementation behaves identically across current browsers.
Use a hypothetical comparison carefully
Suppose two legitimate test configurations differ only in frame rate. Recording each complete configuration and its returned properties gives a meaningful comparison. Recording only the more favourable response does not establish support for the other configuration. The result also cannot answer whether the viewer is signed into the correct service, has a valid media licence or can reach a particular content server.
Follow with an actual playback check
Use an authorised sample matching the intended configuration and observe startup, sustained playback and the relevant output route. Retain errors and performance observations separately from the capability query. An external display, system update or different player implementation can change the environment being assessed. Describe the query as one diagnostic input; do not turn it into an unperformed UK IPTV account test or a universal device certification.