Free tool
Site speed check
How fast your server answers, how heavy the page is, and which of the four usual causes of a slow site is yours. No sign-up, nothing stored.
What this measures, and what it does not
It requests your homepage from a datacentre and reads the HTML that comes back. That tells you how quickly your server answers, how big the document is, how much is blocking the page from rendering, and how the images are set up. Those are the four things behind most slow small-business sites.
It is not a full page load. It does not run a browser, so it cannot tell you Largest Contentful Paint or what somebody on a phone on mobile data actually experiences. For that, run your site through PageSpeed Insights, which does load it properly. This is the faster first look, and it finds the causes rather than the symptom.
For context, when we measured 300 local business sites, the median one sent 145 KB of HTML and made 63 requests. Our own previous site sent 731 KB before a single image loaded, which is written up here.