Frequently Asked Questions
Is Site Speed Check really free?
Yes — completely free, no signup, no credit card, and no rate limits. We run it because we use it ourselves when diagnosing slow client sites. Ads on the page help cover hosting, but the tool itself will always be free to use.
What are Core Web Vitals?
Core Web Vitals are a set of three metrics Google uses to measure real-world user experience: Largest Contentful Paint (LCP) measures how long the main content takes to render, Cumulative Layout Shift (CLS) measures how much the page jumps around as it loads, and Interaction to Next Paint (INP) measures how responsive the page feels when users interact with it. Together they're a direct factor in search rankings, not just a nice-to-have.
What's a good LCP score?
Google's thresholds are 2.5 seconds or less for "Good," 2.5 to 4 seconds for "Needs improvement," and over 4 seconds for "Poor." If your LCP is above 4 seconds, that's your top priority to fix — it's almost certainly hurting both your search rankings and your conversion rates.
Why is my LCP slow?
The most common causes are a slow server response (high TTFB), a large hero image that isn't optimised, render-blocking JavaScript or CSS, or client-side rendering that delays the first paint. Our report identifies which of these is the biggest contributor on your specific page, so you know exactly what to tackle first.
What's TTFB and why does it matter?
Time To First Byte is how long it takes for the server to start sending the response after the browser requests a page. It's the foundation everything else builds on — you can optimise images, compress CSS, and lazy-load scripts all you want, but if TTFB is 2 seconds your LCP will never be under 2.5. Target under 600ms, ideally under 200ms.
How is this different from Google PageSpeed Insights?
PageSpeed Insights is excellent and we recommend using both tools. The difference is workflow: PSI can be slow to load, overwhelms you with dozens of audits at once, and is sometimes hard to interpret. Site Speed Check focuses on the handful of metrics that actually matter, explains them in plain English, and prioritises fixes for you. Use PSI when you need the full exhaustive audit; use us when you want a quick, clear answer.
Do you test on mobile or desktop?
We test both and report them separately. Mobile performance is usually weaker (slower CPUs, worse network conditions) and is the one Google weights most heavily for ranking, so if you only have time to fix one, fix mobile first. Our report highlights the worst-performing profile so you know where to focus.