What is Codec?

A codec encodes and decodes audio and video files - it determines quality and file size

Codec: Simple Definition

A codec (coder-decoder) is software or hardware that compresses and decompresses digital audio or video. The codec determines how a video or audio file is encoded and how much space it takes up.

Every video file you watch uses a codec. When you play a YouTube video, your device uses a codec (H.264 or VP9) to decode the compressed video data and display it on screen in real time.

How Codecs Work

Video codecs compress footage by finding similarities between adjacent frames. Instead of storing every pixel of every frame, they store only the differences between frames. A talking head video with a static background only needs to store the movement, not the entire background in every frame.

The codec you choose determines the trade-off between file size, quality, and compatibility. H.264 is the most compatible. H.265 is 50% more efficient. AV1 is the most efficient but slowest to encode.

Examples of Codec

H.264

The most widely used video codec. Supported by every device. Used on YouTube, Netflix, and Blu-ray.

H.265 (HEVC)

50% better compression than H.264. Used for 4K content. Requires modern hardware.

AAC

The standard audio codec for streaming. Used by Apple Music, YouTube, and most platforms.

AV1

The newest royalty-free video codec with excellent compression. Growing in adoption.

Work With Your Files

Now that you understand the concept, use our free tools to convert, compress, and optimize your files.

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Frequently Asked Questions

What is the difference between a codec and a format?

A format (like MP4) is the container that holds the data. A codec (like H.264) is how the video/audio data inside is compressed.

What codec does YouTube use?

YouTube primarily uses H.264 for HD video and is transitioning to AV1 for better compression. Audio is usually AAC.

How do I know what codec my video uses?

Use VLC media player: right-click the playing video > Tools > Media Information > Codec tab.

Can I play a video without the right codec?

Without the correct codec, your device cannot decode the video and it will not play. VLC media player includes most codecs built-in.

What is the best video codec?

H.264 for compatibility. H.265 for efficiency on modern devices. AV1 for the best compression on web platforms.