Latency, in the context of web performance, is the time delay between a client sending a request and receiving the first byte of a response from the server. It is most commonly measured as Time to First Byte (TTFB), and it serves as a foundational indicator of how quickly a web server begins delivering content to a user's browser.
Latency is not the same as bandwidth. Bandwidth describes how much data can be transferred at once, while latency describes how long it takes for the transfer to begin. A connection can have high bandwidth yet still suffer from high latency, which means large files may download quickly once they start, but the initial wait before anything loads remains frustratingly long. This distinction matters greatly for web performance, where the perception of speed is heavily influenced by how fast a page begins to respond.
Several factors contribute to latency. Physical distance between the user and the server is one of the most significant: data travels at a finite speed through fiber optic cables and network infrastructure, so a user in Tokyo requesting content from a server in New York will inevitably experience more delay than a user located nearby. Network congestion, DNS resolution time, TLS handshake overhead, and server processing time all add to the total latency a user experiences.
Latency and Core Web Vitals
High latency has a direct and measurable impact on Core Web Vitals, the set of metrics Google uses to evaluate page experience. Largest Contentful Paint (LCP), which measures how long it takes for the main content of a page to become visible, is particularly sensitive to latency. When TTFB is slow, the entire rendering pipeline is delayed, pushing LCP scores into ranges that both hurt user experience and can negatively affect search rankings.
Reducing latency is therefore not only a technical concern but also an SEO concern. Sites with consistently low latency tend to achieve better LCP scores, which contributes to stronger performance signals in Google's ranking systems.
How Latency Is Reduced
The two most widely adopted strategies for reducing latency are Content Delivery Networks (CDNs) and edge computing. A CDN distributes cached copies of static assets across a network of servers located around the world, so that users receive content from a geographically nearby node rather than a distant origin server. Edge computing goes further by executing server-side logic at these distributed locations, reducing the round-trip time for dynamic requests as well.
Protocol improvements also play a role. HTTP/2 and HTTP/3 reduce the number of round trips required to establish a connection and begin transferring data, lowering the effective latency users experience even when physical distance remains unchanged.
For developers and SEO professionals alike, monitoring latency through TTFB measurements is a practical starting point for diagnosing slow page loads and identifying where in the request-response cycle delays are occurring.