I am based in the UK but the question is global where it applies.
In the UK if a company holds more than 3% of stock, they must issue an RNS stating their holdings as they have a notifiable interest.
It is possible to go through all old RNS and gain an understanding of the holders with notifiable interest, however, I am interested to know if there is a website or service that does this already.
For example, here is the UK shorts tracker:
Does anyone know if there is an notifiable interest holdings tracker?