I believe it also depends on what state you're working, at least in U.S. According to Joel Spolsky employer owns anything you do on the side in NY whether it's

I believe it also depends on what state you're working, at least in U.S. According to Joel Spolsky employer owns anything you do on the side in NY whether it's related to your office work or not. https://www.joelonsoftware.com/2016/12/09/developers-side-projects/ https://www.joelonsoftware.com/2016/12/09/developers-side-pr...