Time to First Byte
The time between your browser sending a request to the server and receiving the first response. Slow server, poor hosting, or distant server location increases TTFB. It affects all other metrics too.
Thresholds
Why It Matters?
TTFB is the foundation of all other metrics. If the server is slow, the page can't be fast no matter how optimized it is. Good hosting and CDN usage is critical.