Who can see my tweets to a friend?

A while ago I wrote a post about an interesting Twitter behaviour – if you start a tweet with an @<username> only people who follow you & that person can see the tweet (if you unsure see the post which explains it). The question I had today was to find out who is in that list – or put who follows us both on Twitter?

Oddly, I could not find anything (besides some tools that cost money) to do this?! So I built my own awesome little tester you can use below:

For the developers among you who want to see how this all works? Check it out on bitbucket: https://bitbucket.org/rmaclean/twittercoalesce

Known issues:

• My website uses an older version of jQuery, and I use a newer one in this code. If the loading gives an error or gets stuck on the screen, try refreshing the page (seems to solve it).
• If you have too many people shared between the two names - it will break. I am looking into how to solve this. If this happens - loading will get stuck :|
• Twitter limits clients to 150 calls per hour. If the rate limit is exceeded the loading will get stuck.