VP9 is an open-source video codec developed by Google. It is designed to compress video files efficiently, allowing for high-quality video streaming while using less bandwidth compared to older codecs like H.264. This makes it particularly useful for online platforms that require fast loading times and smooth playback. One of the key features of VP9 is its ability to support resolutions up to 4K, making it suitable for high-definition content. It is widely used in various applications, including YouTube, where it helps deliver videos with minimal buffering and improved visual quality.