HTML Checking for Large Sites
Rocket Validator automatically checks your pages on the W3C Validator.
HTML issues tagged as pseudo-element.
The ::file-selector-button has not been recognized by the W3C Validator. This seems to be a bug in the W3C Validator, which has already been reported.
Learn more:
When was the last time you validated your whole site?
Keep your sites healthy checking for A11Y/HTML issues on an automated schedule.