timetofirstcontent

Time to First Content (TTFC) is a web performance metric that describes the interval from the moment a user initiates navigation to a page to the moment the browser renders the first piece of content in the viewport. In practice, TTFC is closely related to the first contentful paint concept, but there is no universal standard definition. Some definitions specify TTFC as the time to first non-empty visual content, such as text or images, appearing in the visible area, while excluding purely decorative or non-rendered elements.

TTFC is typically measured from navigationStart to the start of the first-contentful-paint event reported by the browser’s performance interfaces. Modern web tooling can capture it via the Performance API, PerformanceObserver hooks for paint timings, and analytics or benchmarking tools. Commonly used implementations include Lighthouse reports, Chrome DevTools, WebPageTest, and the Chrome UX Report. The metric is expressed in milliseconds.

Several factors influence TTFC. Network latency and server response times affect how quickly the initial HTML is delivered and parsed. The critical render path, including render-blocking CSS and JavaScript, can delay when content becomes visible. Resource size, caching, and device performance also play roles. Practices that can improve TTFC include reducing or inlining critical CSS, deferring non-critical JavaScript, lazy-loading below-the-fold content, compressing assets, and employing efficient server configurations and caching strategies.

TTFC serves as an indicator of perceived initial load speed, aiding developers in prioritizing work that makes content appear sooner. While related to First Contentful Paint, its exact interpretation can vary by organization, highlighting the importance of clear measurement definitions in performance budgets.