Server Response Time.
Learn what Server Response Time means in modern search and SEO.
The time a web server takes to respond to a browser's initial request — also known as Time to First Byte (TTFB) — a foundational factor in page speed and Core Web Vitals.
Server response time is the time elapsed from when a browser sends an HTTP request to when it receives the first byte of the server's response. It is equivalent to Time to First Byte (TTFB). A slow server response time delays the start of everything else — downloading HTML, parsing content, fetching sub-resources. Google considers a TTFB under 200ms good; above 600ms is poor. Server response time is measured separately from overall page load time because it isolates infrastructure performance from front-end optimisation.
Causes of Slow Server Response Time
Unoptimised database queries are the most common cause — pages that execute dozens of database calls before serving HTML will always be slow. Other causes include: insufficient server hardware or shared hosting limitations; missing server-side caching (every request regenerates dynamic content from scratch); unoptimised server-side code; slow third-party API dependencies in the request path; and geographic distance between the server and the user (mitigated by CDN edge nodes).
Improving Server Response Time
Key improvements include: implementing server-side page caching (Redis, Memcached, Varnish, or plugin-level caching for WordPress); optimising database queries and adding indexes; upgrading server specifications or moving to a dedicated server; using a CDN to serve static content from geographically distributed edge nodes; and minimising synchronous third-party calls in the request-response cycle. For managed hosting, switching from shared to VPS or dedicated hosting often produces immediate TTFB improvements.
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