How can I tell who forked my repository on GitHub?

Is there a way to know who has forked my repository on GitHub? I can see the number of forks, but I'd like to know who forked my repository and what kind of changes they made to it.

I know they can send me a pull request if they're interested in contributing back to my repository, but is there some other way for me to find out who forked my repository?

Clicking the number of forks shows you the full network. From there you can click "members" to see who forked the repo. Example for ExpressJS: https://github.com/expressjs/express/network/members.

now you can check the forks in Insights -> Forks

One way I discovered from the browser is attempting to create a pull request and then compare across forks. All the existing forks would show up.

The accepted answer above helps to see the accounts who forked the repository. In order to meet the other requirement, i.e. see what kind of changes have been made you will need to go to each individual forked repository and then see the compare tab (please refer to the attached picture). To see exact details on what files have been actually changed you should click on the compare button shown in the image.

The above process is the right way and can be tedious. In case you want to see the summarized information of how ahead or behind is each forked repository you may use the link https://forkinfo.herokuapp.com/, which I have open sourced here in case you want to edit it as per any specific requirements. It fetches information about how much a fork is ahead or behind the parent fork, by getting that information from homepage of each forked repository (from the part highlighted in the image). This information is generated based on comparison of repositories