You see a site you like. You’re pretty sure it’s in WordPress (typing /wp-admin at the end of the url is a good way to check) but- you don’t like reading source code to try to figure things out. Enter:
The What WordPress Theme is That search tool allows you to quickly input a URL and find out what WordPress theme a site is currently using. It can also tell you what parent/child themes are being used along with what plugins are installed.
Source: 30+ Free Pro Resources for Building Killer WordPress Websites in Way Less Time
Hopefully, some developer didn’t rename someones theme as there own- for the clients sake. Child themes are critical to keeping sites up to date and working correctly. If there is one thing we’ve learned from over 10 years of developing on the platform is that it changes.