Regex to match all subdomains of a matched domains

This one should suit your needs:

https?://([a-z0-9]+[.])*sub[12]domain[.]com

• Visualization by Debuggex
• Demo on RegExr

I'm assuming that don't want the subdomains to differ simply by a number. Use this regex:

(^https:\/\/(?:[\w\-\_]+\.)+(?:subdomain1|subdomain2).com)

The single capture group is the full URL. Simply replace subdomain1 and subdomain2 with your actual subdomains.

I tested this on regex101.com