according to brave search summariser:

Nostr protocol defines a way to generate proof of work (PoW) on the client side, allowing relay and client to filter events based on difficulty. Nostril is a command-line tool that can produce a message with proof of work.(1) Proof of work can be generated for GitHub Gist ID, Twitter ID, Mastodon post ID, and Twitter ID. A Proof of Work Service Provider for Nostr is being developed, allowing client apps to request remote PoW generation for event_ids before signing and publishing. (2) The protocol also provides a mechanism for user-driven search, and a NIP defines a way to generate and interpret PoW for Nostr notes. (0)

🌐 nostradamic.com 0
🌐 stacker.news 1
🌐 github.com 2