Bitcointicker.co provides a very slick, very active display that purports to be all the ask/bid transactions on several exchanges (Gemini, Kraken, Coinbase, and others).
Where does it get its data? AFAIU all the bitcoin transactions inside an exchange are just bookkeeping they do and the only real blockchain-recorded transactions are when you send bitcoin into the exchange, take bitcoin out of the exchange, and all the balancing activity the exchange needs to do to buy and sell actual bitcoin to keep themselves balanced. So none of these can be actual bitcoin-network transactions (appearing in the mempool), right?
Only thing I can think of is that somehow when you become an SEC regulated exchange you've got to provide public visibility to the market - just like the NYSE or Nasdaq. Is that the case? Or is it something else?
I do see from the tag
ticker that different exchanges provide different APIs for this. So my actual question is: Why? Are they required to? Because if it isn't a (legal, regulatory) requirement on them I can't see why they do it.