Retain the configuration behind the answer
A query can include details such as media type, dimensions, rate and frame rate. An answer for one set of values cannot be transferred silently to a higher-resolution or higher-frame-rate source. Store the requested configuration with the result so a later reader can see what was actually asked.
For example, a prediction for a hypothetical 720 p 30 configuration is not evidence about a 2160 p 60 version using another codec. The application can compare several complete candidates, but it should not combine the positive fields from different queries into an imaginary configuration none of them described.
Read the three fields independently
Supported addresses whether decoding is possible. Smooth concerns the specified frame rate without needing dropped frames, and powerEfficient concerns energy-efficient playback. MDN also describes initial reporting behaviour before device statistics have been recorded, which is a reason to keep prediction distinct from measured performance.
A result can support a selection policy without proving battery life in hours. Actual power consumption also depends on the screen, radios, other applications and usage. Do not turn a true field into a claim that one service saves a fixed percentage of battery or that the highest resolution is always the best choice.
Verify the viewing outcome separately
A developer should still handle failure after selection and record whether the chosen media played successfully. Delivery throughput, authorisation and display output are not solved by a decoder-capability query. A supported configuration can fail when its media cannot be retrieved.
For an accountable comparison, keep configuration, browser and device context, returned fields and observed playback as separate records. The selection can favour the viewer's needs, such as smooth motion or lower energy use, while preserving a supported fallback. Avoid publishing one generic compatibility badge without the conditions that made the prediction meaningful.
Questions about this guide
Does supported imply the network can deliver the media?
No. Decoding capability and delivery are separate.
Does powerEfficient measure battery life for a whole session?
No. It is a capability result for the supplied configuration, not an hours-of-use measurement.