How do I check if a website is slow?
The subjective vs objective measurement of slowness
'Slow' is partly subjective — a page that takes 2 seconds to display its main content might feel fast in a desktop browser on broadband and painfully slow on a phone with a patchy signal. Rather than relying on how a page feels when you load it on your own fast machine, objective performance tools measure specific metrics: Time to First Byte (how long your server takes to start responding), First Contentful Paint (when any content first appears), and Largest Contentful Paint (when the main piece of content is fully loaded). Google's 'Good' threshold is an LCP under 2.5 seconds — if you're consistently above that, users are experiencing a slow site.
What to look for in the Network tab
Browser developer tools' Network tab (opened with F12 in most browsers) shows every resource loaded on the page: HTML, CSS, JavaScript files, images, fonts, and third-party embeds. Each one has a corresponding load time bar. The things to look for: any resource with an unusually long load time (a particularly large image, an external third-party script taking hundreds of milliseconds), the total page weight at the bottom, and the time until 'load' fires (the point at which all resources have loaded). This view tells you both how slow the page is overall and specifically which resources are contributing most to that slowness.
Testing under realistic conditions rather than ideal ones
Testing a page from your own fast broadband connection and seeing it load in 0.8 seconds doesn't represent the experience of a visitor on a mid-range phone with an average mobile connection. Google's Lighthouse tool (built into Chrome developer tools, also accessible via PageSpeed Insights) simulates a slower mobile connection by default — which is more useful for understanding real-world performance. The Core Web Vitals field data in PageSpeed Insights, drawn from actual Chrome user visits, is the most reliable indicator of what real visitors are experiencing on your site.
Key Takeaways
- 'Slow' needs objective measurement — rely on LCP (under 2.5s = good) not your own perception.
- The F12 Network tab shows exactly which resources are contributing most to load time.
- Test under simulated mobile conditions, not your own fast broadband connection.