HEVC

HEVC stands for High Efficiency Video Coding, and its ITU-T recommendation is H.265. It followed H.264, also called AVC, and reaches similar quality at a lower bitrate. It is common in cameras, phones, Blu-ray discs at 4K and many video files, and it is one of the codecs a graphics chip's decoder may handle in fixed-function hardware.

Browser support for HEVC is less even than for H.264, and it depends on the browser, the operating system and the hardware together. That is why the question to ask is not whether a browser plays HEVC in general, but whether it offers a decoder at the size and frame rate you need. The video decode test asks with a full codec string, such as hvc1.1.6.L153.B0 for Main profile at 4K and 60 fps, preferring hardware and then software, and times a decode where the browser can also encode HEVC to make a clip.

Where the browser cannot encode HEVC, there is no clip to time, and the test reports the browser's answers on their own. If HEVC files will not play in the browser at all, a native player may still play them through a different decoder path, so the browser's answer describes the browser only.