Server response time is how long a server takes to start sending back a page after it receives a request.
Server response time is the delay between a browser asking for a page and the server beginning to answer. During that time the server receives the request, runs any code needed to build the page, fetches data from the database and starts sending the first bytes of HTML back.
It's closely related to TTFB (time to first byte). TTFB measures the whole wait from the visitor's side, including DNS lookup, connection setup and network distance. Server response time is the part of that wait spent on the server itself.
What is a good server response time
Google's PageSpeed Insights flags an initial server response time above about 600 milliseconds as something to fix. As a rough guide:
- Under 200 ms: fast. Typical for cached pages on a good host.
- 200 to 600 ms: acceptable for dynamic, uncached pages.
- Over 600 ms: slow enough to drag down page speed and Core Web Vitals.
Because the browser can't start loading images, styles or scripts until the HTML arrives, every millisecond here delays everything else.
What affects server response time
- Caching: a page served from a full-page cache skips PHP and the database almost completely.
- Application code: heavy themes, slow plugins and inefficient queries.
- Database speed: missing indexes, a bloated database or no object cache.
- Server hardware: CPU speed and storage type, such as NVMe.
- Web server software: event-driven servers like LiteSpeed handle many connections efficiently.
- Resource limits: if your account is at its resource usage limits, requests queue.
- Traffic and bots: sudden spikes can saturate available PHP workers.
How to measure server response time
Run your page through PageSpeed Insights or a similar speed test and look at the server response or TTFB figure. From a terminal you can use curl -o /dev/null -s -w "%{time_starttransfer}\n" https://example.com. Test several times and from different locations, and compare a cached page with an uncached one, such as a logged-in page or a search.
How to improve server response time
- Turn on full-page caching, for example LiteSpeed Cache on WordPress.
- Add an object cache like Redis for dynamic pages.
- Enable PHP OPcache and use a current PHP version.
- Remove slow plugins and clean up the database.
- Use a CDN to serve cached pages and files closer to visitors.
- Upgrade your hosting if your site regularly hits its resource limits.
Server response time is just one part of page speed. Large images, heavy scripts and render-blocking styles still need attention once the server is fast.