In this article
After reading, you'll understand:
- What a codec is and how it differs from a container
- How H.264, H.265 and AV1 compare on efficiency and support
- Audio codecs, and how they pair with video
- Why platforms transcode into several codecs
What is a codec?
A codec (coder–decoder) is the algorithm that compresses video into a manageable size for storage and streaming, then decompresses it for playback. Raw video is enormous — far too large to stream — so every video you watch online has been through a codec.
A codec is not the same as a file format. The codec encodes the actual video and audio; the container (MP4, MOV, WebM) is the wrapper that holds the encoded streams plus metadata and subtitles. An MP4 file typically carries H.264 video and AAC audio inside it — two codecs, one container.
The codec choice drives the trade-off at the heart of streaming: better compression means smaller files and lower bitrate for the same quality, but often at the cost of heavier encoding and narrower device support.
The common video codecs
| Codec | Also known as | Efficiency | Support | Notes |
|---|---|---|---|---|
| H.264 | AVC | Baseline | Universal | The safe default |
| H.265 | HEVC | ~2× H.264 | Broad | Licensing cost; 4K-friendly |
| AV1 | — | Best; royalty-free | Growing | Heavy to encode |
| VP9 | — | ~H.265; royalty-free | Broad (web) | Common on YouTube |
H.265 and AV1 reach similar quality at roughly half the bitrate of H.264 — the reason large platforms invest in them despite higher encoding cost.
Audio codecs
Video always ships with an audio codec alongside it, and the same efficiency-vs-support logic applies:
| Codec | Efficiency | Where it's used |
|---|---|---|
| AAC | Standard | HLS and most web video — the default |
| Opus | Better at low bitrates; royalty-free | WebRTC, WebM |
| MP3 | Older, less efficient | Legacy / audio-only |
Just like video, the platform picks an audio codec the target device can decode — you don't choose it by hand.
How Kinescope handles this
You don't pick a codec on Kinescope. Transcoding runs automatically on upload, producing the right video and audio codecs and renditions, and each viewer is served the best version their device supports — packaged into HLS (and DASH for DRM) and delivered from the global CDN. Upload a common format; the platform handles the rest.
Read the Kinescope docsFrequently asked questions
What is the difference between a codec and a container?
A codec compresses and decompresses the video and audio streams (H.264, H.265, AV1). A container — like MP4, MOV or WebM — is the file wrapper that holds those encoded streams together with metadata and subtitles. An MP4 file, for example, commonly contains H.264 video and AAC audio.
Which video codec should I use?
H.264 (AVC) is the safe default — universally supported and efficient enough for most needs. H.265 (HEVC) and AV1 achieve similar quality at roughly half the bitrate, saving bandwidth, but have narrower device support and higher encoding cost. Most platforms transcode into several so each viewer gets the best codec their device supports.
Is H.265 better than H.264?
For compression, yes — H.265 (HEVC) delivers similar quality at about half the bitrate, which cuts storage and delivery costs. The trade-offs are more expensive encoding and licensing, plus slightly narrower device support. AV1 pushes efficiency further and is royalty-free, but is heavier to encode.
What is AV1?
AV1 is a modern, royalty-free video codec developed by the Alliance for Open Media. It offers better compression than H.265 with no licensing fees, which is why streaming giants adopt it — at the cost of significantly heavier encoding. Device and browser support is growing steadily.
What audio codec goes with streaming video?
AAC is the standard audio codec for HLS and most web video — efficient and universally supported. Opus is a newer, royalty-free codec with better quality at low bitrates, common in WebRTC and WebM. As with video, the platform picks an audio codec the target device can decode.
Do I need to pick a codec on Kinescope?
No. Kinescope transcodes your upload into the appropriate codecs and renditions automatically, then serves each viewer the best supported version. You upload a common format and the platform handles codec choice, packaging and delivery.
Further reading
- Video codec — Wikipedia — a vendor-neutral overview.
- Alliance for Open Media — AV1 — the AV1 codec project.
