RandomX

With micropayments, the server owner makes 1 million requests times 0.05 cents = ~$500 The status quo with those js PoW pages doesn't really benefit the server owner at all, it's wasted energy. I mean proof of work is always wasted energy, but I figure it's better to kill two birds with one stone. CoinHive was one example of this. (I think this is a correct link? https://github.com/cazala/coin-hive). Although I think ideally you would want to have some sort of browser plugin or app that runs on bare metal instead of a proof-of-work in the browser, because RandomX is designed such that it's slow when implemented in JS (https://github.com/tevador/RandomX/blob/master/doc/design.md)

Monero's RandomX is an interesting PoW scheme one designed to be optimized for CPUs. Here is an interesting read about its design https://github.com/tevador/RandomX/blob/master/doc/design.md Chia uses a very memory-hard PoW system and is usually mined on SSDs. I've seen a lot of "useful PoW" cryptocurrencies, but they tend to not pan out. For example Gridcoin is just a Proof-of-Stake cryptocurrency with a program that hands out GRC to BOINC contributors.