Single-Page Application (SPA)
A Single-Page Application (SPA) is a modern web application that loads a single HTML page and then dynamically updates the content as the user interacts with it, offering a fluid, app-like user experience. Instead of performing full page reloads, SPAs use JavaScript to rewrite the current page, a process known as a Soft Navigation. While this can feel smooth to the user, this architecture creates a "measurement blind spot" for many standard performance tools. Core Web Vitals are often only measured for the initial page load, completely missing the performance of subsequent views loaded via soft navigations. This makes it difficult to diagnose performance issues that occur deep within a user's session.
Related web performance terms
- Search Engine Optimization (SEO)
SEO is the process of improving a website's visibility in search engine results pages (like Google). The goal is to rank higher than competitors for relevant search queries to attract more organic (free) traffic.
- Server Response Time
Server Response Time is a component of Time to First Byte that measures how long the server takes to process a request and start sending back a response, excluding network latency.
- Server Timing
Server Timing is a browser API that allows the backend to communicate performance metrics about its own internal processes (e.g., database query time, time to render a component) to the browser via HTTP headers.
- Server-Side A/B Testing
This is a performance-friendly method for running A/B tests. Unlike Client-Side A/B Testing, the decision of which variation to show a user is made on the Origin Server.