How to know BTC balance of certain addresses at a certain block height?

[100bitcoin]

Looking for some online tool or api...

[Coding Enthusiast]

https://api.blockcypher.com/v1/btc/main/addrs/$Address?limit=2000
The response will be in JSON, look for the key "txrefs" which is an array of transactions that contain hash, block height, ... Then it's just a matter of putting the result in an array and then filtering the result based on whatever block height number or datetime you want.

I am doing it this way in my little project. In the ForkBalance window you can update the tx history and by setting the height to whatever it will calculate the balance of the address at that height.