In this guide
Describe the actual configurationInterpret the three properties independentlyA reported assessment has limitsThe Media Capabilities API can assess a described decoding configuration through decodingInfo. Its result separates whether the configuration is supported, expected to be smooth and considered power efficient. These are different questions.
A configuration includes more than a codec family name. Video characteristics such as dimensions, bit rate and frame rate can change the assessment. The result belongs to the queried browser/device context, not to every device sharing a brand or operating system.
Describe the actual configuration
The input specifies a media decoding type and valid audio and/or video characteristics. A malformed MIME description or missing required information can produce an error instead of a useful capability answer. A successful query for a small low-rate video does not establish the result for a larger high-frame-rate rendition.
An original hypothetical comparison asks about the same codec at 1280×720/30 and 3840×2160/60. Even though the codec family is identical, the requested workloads differ substantially. They should be retained as separate observations.
Interpret the three properties independently
| Property | Question |
|---|---|
| supported | Can the described configuration be decoded? |
| smooth | Can the stated frame-rate workload be handled without expected frame dropping? |
| powerEfficient | Does the browser assess this path as power efficient? |
| Actual playback | What happened under the current media and operating conditions? |
A reported assessment has limits
Browser implementations may use available device knowledge and recorded statistics; the documented result should not be converted into a hardware-decoder certificate. Power efficiency is not a direct battery-life measurement. Smoothness is not a guarantee that network delivery, media validity or rendering conditions will remain suitable.
Record the full queried configuration, browser version and result. Compare actual frame counters and buffer behavior when diagnosing real playback. Do not infer a protected-content entitlement or a service’s device support from this API; content protection and permission have separate requirements.
The most useful application is choosing among accurately described alternatives and preserving clear evidence when the observed result differs from the assessment.