The law says you need to be covered by a TV Licence to:
- watch or record programmes as they’re being shown on TV, on any channel
- watch or stream programmes live on an online TV service (such as ITV Hub, All 4, YouTube, Amazon Prime Video, Now TV, Sky Go, etc.)
- download or watch any BBC programmes on iPlayer.
This applies to any device you use, including a TV, desktop computer, laptop, mobile phone, tablet, games console, digital box or DVD/VHS recorder.
And
What is live TV and when do I need a licence for it?
Live TV means any programme you watch or record as it’s being shown on TV or live on any online TV service. It’s not just live events like sport, news and music. It covers all programmes on any channel, including soaps, series, documentaries and even movies.
If you’re watching live TV, you need to be covered by a TV Licence:
- if you’re watching on TV or on an online TV service
- for all channels, not just the BBC
- if you record a programme and watch it later
- if you watch a programme on a delay
- to watch or record repeats
- to watch or record programmes on +1, +2 and +24 channels
- to watch live programmes on Red Button services
- even if you already pay for cable, satellite or other TV services
From the TV Licensing body.
Basically, if its playing solely because you hit the play button, its not “live TV” and you dont need a license to view it.
If it would be playing at the same time for everyone on a schedule rather than on demand, its live TV.  This includes sports on streaming services.
So, a Youtube video you can view at any time is not live TV, but a Youtube video you have to see at a certain time is.  A subsequent recording of a live stream that you did not make is not live TV for the purposes of licensing.
A Twitch or Facebook livestream would also require a TV license to view.