There are a lot of different services claiming to analyse the speed of your website. Out of these we recommend two.
The first we recommend is provided by webpage test to measure the performance of your site. This tool provides very detailed performance information with the ability to choose the location of the request.
The second we recommend is running google Lighthouse from within the Chrome browser on your local computer. Running it locally is important, using the online pagespeed insights will result in the test being run from the US with simulated slowdowns which might not be reflective of your clients.
For more detailed instructions on how we would test the speed of a website we have a detailed guide coming soon....