Regex tester bug

Describe the bug

The following phone number regex seems to not work properly: ^(?\d{3})?(\s|-)?\d{3}(\s|-)?\d{4}$ I'm running it against a string of just 10 digits and it's mandating a space or hyphen for (\s|-)? when the ? should allow it to be optional.

What happened?

System information

Windows 11, Vivaldi and Chrome

Where did you encounter the bug?

Public app (it-tools.tech)