html5pattern.com no longer exists but leads to a suspicious site
A ProcessWire Text Field can optionally have a Pattern, defined on its Input tab when editing the field in the admin.
Currently the option has the "Notes":
See html5pattern.com for examples of patterns you can use and create.
However, html5pattern.com no longer exists and the link leads to a suspicious site.
I did not find an alternative site to recommend, but maybe recommending both MDN and Regexlib is a good alternative: https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Attributes/pattern and https://regexlib.com/
The new notes could be:
See MDN for HTML pattern attribute details and browse regex examples at RegexLib.
@szabeszg, this is already fixed in https://github.com/processwire/processwire/commit/421a88c31bd65e92e154322114f0b5fafa92c61a, but I'll leave it open if Ryan decides to add a RegexLib link.