Calculating exchange reserves/inflows/outflows I see that there are a few sites that provide analytics for this kind of data (here's one:
https://www.tokenanalyst.io/dashboard).
I'm wondering how these companies are able to track this information.  Are the addresses of major exchanges publicly known?  Do the exchanges publish or offer this data?
Most exchanges aren't publishing this data, some even trying to hide as much of it as possible, using separate wallets and trying to be smart about change progression.
A lot of the analytic companies are using repositories (examples:1, 2) of publicly known addresses to find out the wallet ownership.
But this isn't the most optimal solution when it comes to analytics, some blockchain analytic companies are actually applying as customers of these exchanges and trying to get on-chain activity, main addresses (so-called hotwallets) and marking wallets through common input clustering.