The only browser with native support for Regex searches I was able to find is Konqueror. It's available onley for Linux systems.
You should rely on a plugin, for example:
- Chrome Regex Search extension for Google Chrome
- found nothing for Safari
- Regex Search add-on for Mozilla Firefox
You can use RegEx search in Google Chrome DevTools, typing Ctrl + Shift + F on Windows or Command + F on Mac, but it will search in the code and not for the page content only.