Basically, Youtube ( aka youtube.com and googlevideo.com ) are exclusively viewable through the HTTPS protocol
When browsing the Internet through the proxy and on HTTPs/SSL sites, the proxy is not able to read the content of the data.
It is able to know the source, i.e. the sites you visit and the source, the address of the clients that carry the browsers.
Basically without SSL inspection at the proxy level, youtube or any other SSL website cannot be cached.
So, if you really want to cache youtube videos and sites, it is imperative to do SSL decryption at the proxy level
If you are an ISP YES but Google has a dedicated offer for this purpose.
In addition, you will have to deploy the SSL certificate in all browsers, which puts a huge strain on the infrastructure.
If you are using Artica for your network, please note the following before making such a decision:
In most cases, videos are played only once, with the exception of music videos where you can replay a song.
Caching a video after it has been played is of little use since the local cache is only effective after the video has been retrieved.
Of course, the more users you have, the more likely it is that a video will be requested by multiple people (if and only if those people have the same desires).
The Youtube javascript client adapts to the bandwidth.
Depending on the quality of your bandwidth, the quality of the video will adapt dynamically and therefore the proxy can cache the video files according to the bandwidth.
Thus a video can be played in 4k and then in 600dpi, or even 400dpi, so the proxy can potentially store 3 videos for one.
This consumes dramatically hard disk and limits the benefits because once hidden, only 4K videos will be requested because the bandwidth will be local.
In conclusion, with the obligation to decrypt Youtube and its constraints and the few benefits once this operation is done, if your motivation is to keep free bandwidth while providing access to Youtube, the best strategy is to force the Youtube javascript client to use the video with the least volume.
The bandwidth limitation feature in the proxy will reduce the Youtube stream on your clients and will force to use 600 or 400dpi videos.
This is not a small thing:
A 4K video is several hundred Mb while a 400dpi video is a few Mb.