A tool to download all a user's twitter followers
Ensure you have go installed:
# e.g. on a Mac
brew install go
Install the twitter-followers script:
go install github.com/ConradIrwin/twitter-followers
twitter-followers <screen_name>
This will output a json object per line for each follower. It uses the same ordering as the Twitter API, which is approximately reverse chronological order of when they followed you.
I suggest pairing this with jq to extract the fields you need.