Video Codecs Explained: H.264, HEVC, VP9, and AV1

A codec is the algorithm that turns raw frames into a compressed bitstream and back. Choosing one is a balance of three forces that rarely point the same way: compression efficiency, licensing cost, and device reach. This article walks through the four video codecs you will actually ship in 2026, plus the two audio codecs that pair with them.

H.264 / AVC — the universal baseline

Standardized in 2003, H.264 (also called AVC) is the most widely supported video codec in history. Essentially every browser, phone, smart TV, and set-top box decodes it, very often in hardware.

• Efficiency: the reference point everything else is measured against.
• Licensing: royalty-bearing via the MPEG LA / Via LA patent pool, though terms are well understood and broadly paid into.
• Codec string: avc1.PPCCLL, where the bytes are profile, constraints, and level. For example avc1.640028 is High profile, level 4.0; avc1.42E01E is Baseline level 3.0.

If you can ship only one codec, it is H.264. It is the safe floor of every bitrate ladder.

H.265 / HEVC — better, but tangled

HEVC (2013) delivers roughly 40–50% bitrate savings versus H.264 at similar quality (an approximate, widely cited figure that varies by content). It is the workhorse of 4K and HDR.

• Efficiency: clearly better than H.264, especially at high resolutions.
• Licensing: notoriously fragmented across multiple patent pools, which slowed web adoption for years.
• Device support: strong on Apple platforms and modern TVs; no native support in Chrome or Firefox on the desktop web, which is its biggest gap.
• Codec strings: hvc1.* (parameter sets in the sample description, required by Apple) or hev1.* (parameter sets inline). For HLS to Apple devices, prefer hvc1.

Use HEVC where you control the device — Apple ecosystems, native apps, and TV platforms — and where 4K/HDR efficiency justifies a second encode.

VP9 — Google's royalty-free answer

VP9 (2013) is royalty-free and reaches efficiency in the same ballpark as HEVC. It powers most 4K on YouTube.

• Efficiency: comparable to HEVC, codec-dependent and content-dependent.
• Licensing: royalty-free.
• Device support: native in Chrome, Firefox, Edge, and Android; not on Safari/iOS, and hardware decode is less universal than H.264.
• Codec string: vp09.PP.LL.DD, e.g. vp09.00.10.08 (profile 0, level 1.0, 8-bit).

VP9 is a natural fit when your traffic skews toward Chrome/Android and you want to avoid HEVC's royalties.

AV1 — the current efficiency leader

AV1 (2018, from the Alliance for Open Media) is royalty-free and offers roughly 30% better efficiency than VP9/HEVC on typical content — again an approximate, content-sensitive figure.

• Efficiency: best of the group, especially at low bitrates.
• Licensing: royalty-free, backed by Google, Netflix, Amazon, and others.
• Device support: growing fast — modern Chrome/Firefox, Android, recent GPUs, and an increasing share of new TVs and the latest Apple silicon. Older hardware lacks AV1 decode, so software fallback can be CPU-heavy.
• Codec string: av01.P.LLT.DD, e.g. av01.0.08M.08 (profile 0, level 4.0 Main tier, 8-bit).

AV1 encoding is expensive in CPU time, but encoders like SVT-AV1 have made it practical. Use it as a top tier for high-volume VOD where bandwidth savings repay the encode cost.

Audio: AAC and Opus

Video almost never travels alone.

• AAC is the universal audio codec, the counterpart to H.264. It plays everywhere and is the default for HLS and most VOD. Codec string mp4a.40.2 (AAC-LC) or mp4a.40.5 (HE-AAC).
• Opus is royalty-free, highly efficient at low bitrates, and excellent for speech and low-latency/WebRTC use. It pairs naturally with VP9/AV1 in WebM but is not supported on Safari/iOS for HLS, so AAC remains the safe default for broad reach.

Choosing in practice

A pragmatic 2026 strategy:

• Always ship H.264 + AAC as the compatibility floor.
• Add HEVC for Apple and TV apps that need efficient 4K/HDR.
• Add VP9 or AV1 for the modern web and high-volume titles where bandwidth savings matter, with AV1 as the top tier when device support and encode budget allow.

Codec strings appear directly in HLS CODECS attributes and DASH Representation elements, so getting them right is what lets a player decide whether it can play a rendition before downloading it. You can verify the codec, profile, and level of any file with the media info inspector, and inspect how those strings are declared in a manifest on the player and manifest tools.

For the perceptual fundamentals behind these efficiency gains, see Video Compression Basics; to learn how you actually produce these encodes, continue with Transcoding Explained.