FCP

FCP (First Contentful Paint) marks the moment the first meaningful pixel — any text or image — is painted on screen. It's used as a diagnostic companion to Core Web Vitals: a healthy LCP usually pulls FCP into a healthy range too.

Slow FCP almost always points to one of two issues: render-blocking resources (heavy fonts, CSS) or a slow server response, i.e. high TTFB. That's why teams typically read FCP and TTFB together rather than separately.

Don't confuse it with LCP. FCP is 'first thing visible'; LCP is 'largest meaningful thing visible'. Looking at both is the only way the numbers match up with perceived speed.