Time to First Byte (TTFB) measures how long it takes for the server to start sending data back to the browser after a request is made. It includes DNS lookup, TCP connection, SSL negotiation, and server processing time.
TTFB thresholds
- Good: 800 milliseconds or less
- Needs Improvement: Between 800 and 1800 milliseconds
- Poor: More than 1800 milliseconds
What affects TTFB
- Server processing time
- Network latency
- DNS resolution time
- SSL/TLS negotiation
- CDN configuration
Improving TTFB
- Use a CDN to serve content closer to users
- Optimize server-side code
- Use efficient database queries
- Implement caching strategies
- Upgrade hosting infrastructure
Related Terms
First Contentful Paint (FCP)
A performance metric that measures the time from when the page starts loading to when any part of the page's content is rendered on screen.
Largest Contentful Paint (LCP)
A Core Web Vital that measures how long it takes for the largest content element visible in the viewport to render.
Latency
The time delay between a user action and the system's response, often referring to network delay in web performance.
Server Response Time
The time it takes for a server to respond to a request from a browser, measured from request initiation to receiving the first byte of response.