well technically you can see it on the orderbook, for example on a certain price there is X amount of bitcoin being sold or bought, or on the depth chart.

some exchanges are also giving the "orders" in their API call, for example the API call returns a list of all orders at some price.
something like this:
{
  "price":1500,
   "orders":
               [ 
                 "size" : 0.001 ,
                 "size" : 100,
                 "size" : 123.21335,
                 ...
               ]
  "price":1501,
   "orders":
               [...]
}