> Take for example nitter - it says its using an unofficial twitter API. I'm assuming this means its using one of these third party services that provide an API

> Take for example nitter - it says its using an unofficial twitter API. I'm assuming this means its using one of these third party services that provide an API You misread that. It actually says: Uses Twitter's unofficial API (no developer account required) In other words, it's an internal Twitter API that's not meant to be used for applications like this.