You've found a contributor whose work you depend on. The maintainer of a package you use, a developer who fixed something for you upstream, the author of a CVE you need to coordinate with. You have their GitHub username. You'd like their email. You'd think this would be a GET away. It isn't. Here's why — and what it actually takes to find one. The GitHub API doesn't have it GET /users/:login returns an email field. For the vast majority of users, that field is null . GitHub flipped private-by-default years ago. When you sign up today, your commit email is set to <id>+<login>@users.noreply.github.com and the public profile email field is empty. Older accounts that opted in still expose addresses, but they're a minority — and the people you actually want to reach (active maintainers, security-conscious developers) are exactly the ones who turned this off. So that's out. The commits don't have it either (mostly) The next obvious move: look at the user's commits.…