Twitter offers the ability to archive your tweets and other data they keep about you, but that archive doesn't include alt text. This tool will take an archive zip file or the extracted tweets.js and scrape twitter for all the alt text you've ever written. It will return everything in a JSON file for future work to incorporate with the downloaded archive. For now it also offers
https://archive.alt-text.org/search, which will allow fuzzy searching of the alt text you've written.