Streaming Codecs Explained (H.264 / H.265 / AV1)
Codecs determine video quality and bandwidth usage. Knowing which codec a streaming service uses explains why one plan looks better than another at the same resolution.
Codecs determine video quality and bandwidth usage. Knowing which codec a streaming service uses explains why one plan looks better than another at the same resolution.
What is a Codec, Practically Speaking?
A codec is a compression-and-decompression algorithm — the thing that takes a 4K video file (which would be about 1TB per hour raw) and squishes it down to something you can actually stream over a home internet connection (about 15-25GB per hour at Netflix 4K quality). Better codecs hit the same visual quality at smaller file sizes, which means less buffering, lower bandwidth usage, and sharper picture on shaky mobile connections. If you've ever wondered why Netflix on your 2019 phone looks worse than Netflix on a 2023 phone at the 'same' resolution, the answer is almost always codec support — the newer phone decodes AV1, the older one falls back to H.264. The three codecs to know are H.264, H.265 (HEVC), and AV1, and they account for roughly 95% of all video streaming worldwide.