We recently wrote an article explaining how to enable GPU hardware acceleration in your browser to reduce the load on yor CPU. That got us to thinking about what YouTube commonly uses three primary video codecs for delivering content, each with different characteristics and levels of adoption:
- H.264 (also known as AVC – Advanced Video Coding):
- First Released: 2003
- Significant Revisions: Yes, numerous. H.264 has been continually developed and revised through various “profiles” and “levels.” Key profiles like High Profile (HiP) were introduced to support higher resolutions and bitrates (common for HD content), and further profiles like High 10 Profile and High 4:2:2 Profile extended support for higher bit depths and chroma subsampling. While the base codec name remains H.264, these revisions define the specific features and complexity supported.
- Developed by: ISO/IEC MPEG and ITU-T VCEG
- Characteristics: This has been the industry standard for a long time. While less efficient in terms of compression than VP9 or AV1, it boasts universal compatibility. Almost every device and browser can hardware-decode H.264 efficiently. It requires licensing fees, but these are generally covered by content distributors like YouTube
- When YouTube uses it: YouTube still encodes virtually all videos in H.264, primarily for maximum compatibility across the widest range of devices, especially older ones or those without VP9/AV1 hardware decoding capabilities. For videos with lower view counts, H.264 might be the only option provided for higher resolutions (e.g., 1080p). It acts as a reliable fallback
- Hardware Support: Almost all GPUs from the last decade or more have robust H.264 hardware decoders
- VP9:
- First Released: 2013
- Significant Revisions: Less formal “revisions” in the sense of entirely new versions, but continuous improvements and additions. Google often refers to internal versions or profiles for VP9 (e.g., profiles for higher bit depth like 10-bit and 12-bit, or specific chroma formats) rather than discrete “versions” like H.264/H.265. The core VP9 specification has remained stable since its initial finalization.
- Developed by: Google
- Characteristics: It’s an open-source, royalty-free codec that offers good compression efficiency, often comparable to H.265 (HEVC). Google heavily promotes VP9, and it’s widely supported across Google’s ecosystem (Chrome, Android, YouTube itself)
- When YouTube uses it: For a significant portion of its content, especially for HD (1080p) and 4K videos, and generally for videos with higher view counts.
- Hardware Support: Most modern integrated GPUs (like your Intel UHD Graphics 770 in the 12th Gen CPU) and dedicated GPUs have hardware decoders for VP9, making it very efficient when hardware acceleration is enabled
- AV1:
- First Released: 2018 (Final specification published)
- Significant Revisions: Yes. While AV1 is relatively new, its development has continued since the initial specification (Version 1.0.0). AOMedia has been working on future versions (e.g., AV2) and minor updates/refinements to the existing AV1 specification to add features (like screen content coding tools) and further optimize performance and efficiency. For end-users, the “AV1” label typically refers to the main public release standard
- Developed by: The Alliance for Open Media (AOMedia), which includes major tech companies like Google, Netflix, Amazon, Apple, Meta, Microsoft, Intel, and others
- Characteristics: It’s the newest of the three, also open-source and royalty-free. AV1 offers superior compression efficiency compared to both VP9 and H.265 (HEVC), meaning it can deliver similar quality at significantly lower bitrates, which saves bandwidth
- When YouTube uses it: YouTube is increasingly adopting AV1, especially for higher resolutions (e.g., 8K), very popular videos, and for users with compatible hardware
- Hardware Support: Hardware decoding support for AV1 is becoming more common in newer GPUs and CPUs (even 12th Gen Intel CPU’s do support AV1 hardware decode), but it’s not as ubiquitous as H.264 or VP9 yet. Software decoding of AV1 can be very CPU-intensive
Summary:
- AV1 if your device/browser supports hardware decoding and it’s a popular video or high resolution
- VP9 as the next preferred option if AV1 isn’t feasible or available, particularly for HD and 4K content, and for most other popular videos
- H.264 as the universal fallback, ensuring that almost any device can play the video, though it might be limited to 1080p or lower resolutions for this codec, even if higher resolutions are uploaded
The specific codec YouTube serves you for a particular video depends on several factors: the video’s popularity, the resolution you’re requesting, your browser, your operating system, and most importantly, your hardware’s decoding capabilities.
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