For Best Video and Audio Quality:
* MP4 (H.264/AVC codec): This is the most widely supported and versatile format. It offers good compression, meaning it can maintain high quality while keeping file size relatively small. It's also great for streaming.
For Smallest Size (while maintaining decent quality):
* MP4 (H.265/HEVC codec): This is the newer, more efficient codec, offering better compression than H.264. It means you can achieve higher quality at smaller file sizes. However, not all devices and software support HEVC yet.
* WebM (VP9 codec): This format is designed for web video and is known for its efficient compression. It's gaining popularity but may not be as universally supported as MP4.
Here's a breakdown of other options:
* MPEG (MPG): Older format, good for DVD quality but not as versatile or efficient as modern formats.
* AVI: A container format, meaning it can hold different video and audio codecs. Can be bulky and not always compatible with modern devices.
* FLV: Flash video format, used extensively for streaming in the past but less popular now.
* MOV: Apple's video format, often used for high-quality content, but not as widely compatible as MP4.
* WMV: Microsoft's format, can be high-quality but not as popular as MP4.
In Summary:
* For the best balance of quality and size, go with MP4 (H.264 or H.265).
* If you need the absolute smallest file size, explore MP4 (H.265) or WebM.
* Consider your target audience and their devices' compatibility when choosing a format.
Pro Tip: Most YouTube video downloaders and converters allow you to choose the output format and even adjust the quality settings.