A practical guide to YouTube video
Understanding YouTube's format list
YouTube stores a single video many times over. A popular 1080p upload might exist as a dozen separate files: H.264 MP4 at several resolutions, VP9 WebM at several more, AV1 for newer devices, and audio only tracks at different bitrates. The player stitches the right combination together on the fly based on your screen and connection.
That's why our list here is longer than on other platforms, and why the same resolution can appear twice with different sizes. The smaller one is usually VP9 or AV1, which fits more picture into fewer bytes. The larger one is H.264, which plays everywhere. If compatibility matters more than file size, take the H.264.
Choosing resolution without wasting space
Here's a rough guide from real file sizes. A 10 minute video at 720p is around 100 MB. At 1080p it's roughly 200 MB. At 1440p you're near 500 MB, and 2160p can pass a gigabyte. The jump from 720p to 1080p is worth it on any screen bigger than a phone. The jump from 1080p to 4K is only worth it if your display is genuinely 4K and you're sitting close enough to tell.
Length multiplies everything. Saving a two hour documentary in 4K is a several gigabyte commitment and will take a while on a normal connection. For long form talking content, 720p is honestly fine and downloads in a fraction of the time.
The separate audio problem
This confuses people more than anything else on YouTube. Above 1080p, video and audio are stored apart. A 4K download can therefore be completely silent, which looks like a broken file but isn't. The audio exists, it's just a different stream.
You have three options. Take 1080p, which is muxed and includes sound in one file. Download both streams and merge them with ffmpeg using a command like ffmpeg -i video.webm -i audio.m4a -c copy output.mkv. Or decide the resolution isn't worth the hassle. For most purposes the third option is the right one.
Being a good citizen about it
Creators on YouTube are paid by ad views. Downloading a video for offline viewing on a flight is one thing. Systematically saving and re-uploading a channel's work to another platform takes money out of someone's pocket, and it's the single fastest way to get a copyright strike on your own account.
If you want to reference someone's video, a short clip with visible credit and a link is standard practice and usually welcomed. If you want the whole thing offline and you're a regular viewer, YouTube Premium's built in download works without any of this and pays the creator. Our how it works page walks through the general process, and the platform pages for Instagram and TikTok cover their own quirks.
