there has never been any such thing as "whale alert" and there will never be unless all exchanges unite and then alert you whenever a whale deposits a large amount of fiat or bitcoin to buy or sell bitcoin respectively all the while holding his order from going through until they alert you!
otherwise everything else called "whale alert" is just a scam. there is no way to know what a whale is doing. all these tools do is that they simply find some transaction that is large and then alert you as if it is a whale moving bitcoin to the market to dump!
the reality is that 99% of the cases these movements have nothing to do with whales or with exchanges.
There is a telegram group named "Whale alert". They give alerts whenever there is any big sell or buy in any altcoins. However the group was free to join and it was useful if you wanted to know if there is big pump or dump in any coin. But there is no need to pay for this service and if someone ask money for this, just ignore it.
that is better although i still don't see any point in that. you can see it on the exchange itself in the order history which is usually at the bottom of each coin's page. not to mention that you can only find out about it when the whales dump their altcoin for example, in which case it is already too late to act!
even if you wanted to act based on that, setting up a stop loss order that executes automatically is a lot more effective than joining a group or subscribing to an alert.
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Well i can't really argue since i don't have much knowledge, but they are showing the whale movements fo three exchanges. Bitmex, Bitfinex and GDAX.
they are showing their "guess" about who both the source and the destination addresses belong to. for example when they say "a whale moved X amount to GDAX" it may as well be GDAX itself topping up one of their addresses in their hot wallet from one of their cold storage addresses to pay the withdrawals.
you see the blockchain analysis in its most advanced ways that big analysis companies perform for a hefty price is not reliable to begin with. what these sites have access to and use is basic and free chain analysis that is a much poorer version of that and is the least reliable form.
p.s. if you look at some of the amounts the report that is supposedly being dumped by a whale on an exchange you can see how big a lie it is. sometimes they are in the millions. nobody in his right mind trusts an exchange with millions of dollars at once. not to mention that they can never withdraw millions of dollars from bitcoin exchanges without raising red flags on all the banks involved in the transactions and having their account suspended!