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
How VitalSentinel tracks TTFB
VitalSentinel's RUM monitoring measures TTFB from real visitor sessions across geographies and devices, exposing slow origins, bad CDN cache hit rates, and database regressions that synthetic tests miss. When server response times degrade, you find out in hours, not weeks - before slow TTFB cascades into poor LCP and lost rankings.
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.