I wrote a nano tool that tries to extract the #Fediverse accounts of your #Twitter followings: https://fedifinder.glitch.me/

It searches for the patterns @[email protected], [email protected] and host.tld/@user in the screen name, description, location and URL field. It displays them to you in the correct format for easy copying as well as a CSV download that can be imported to #Mastodon.

New version: https://fedifinder-backup.glitch.me/

Fedifinder

Fediverse accounts of your X/Twitter followings

@Luca Thanks, but in my case all the downloaded handles appear to be email addresses...how do I know which are on Mastodon?
@charlesgaba I changed it, so it no longer detects mail addresses (and sadly no malformed fediverse accounts either).