Bitcoind - Getbalance command

[MadGamer]

I searched a lot and apparently, this command is only able to retrieve the balance If you control the address. I want to know how the blockexplorer etc. do it then? I don't necessarily need the code behind it, just want to know what's the trick here?

[achow101]

You can't do it with bitcoind/Bitcoin Core. In order to find the balance of an address, an address index is required. But maintaining an address index is expensive and not that useful since the node does not need it to operate, so one is not maintained. There is no code in Bitcoin Core to build such an address index.

It is important to note that addresses and balances do not exist on a technical level. It requires significant computation to produce balances for all addresses, and requires a lot of additional storage space to store that data.