Today I ran across a strange situation where the dev tools for Chrome and Firefox were reporting different background color values for the same button. They were both reporting that the relevant CSS was in the same location, so it wasn’t a matter of a difference in cascade/priority.

I changed the color value in the CSS file and then used the “Clear all caches” button on the WPEngine settings page of the WordPress dashboard. Still nothing…

So I jumped on a chat with their support team and found out that there is an “advanced cache file” in the wp-content directory. Removing this file will trigger a hard reset of the WPEngine cache, and the “advanced cache file” will be automatically regenerated.

Honestly, I don’t know what that file is doing or why the “Clear all caches” button doesn’t actually reset all caches, but it seems to have worked.

I just wanted to document the existence and purpose of that file, since that’s not where I would have thought to look when troubleshooting a CSS issue.