Facebook and YouTube can easily share the same videos without any problem. The main thing to consider in that case is which host you are using. Some people choose to upload their videos on YouTube and share them via a link on Facebook, or vice versa. It depends on which platform is the most beneficial for your needs.
Instagram is meant to be a platform for smaller videos that last a few seconds to a minute. This means that you should only post short videos on this platform, but you can also easily share them on Facebook and Youtube. Remember that the biggest difference here is te length of the videos on Instagram compared to the other two platforms.
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Ideally, a video should be just as long to convey the message or information and never too long to avoid boring the audience.