What services do you use to measure website loading speed and why?

Question

Performance evaluation

What services do you use to measure website loading speed?
The main types are Google PageSpeed ​​Insights and Lighthouse in the console.
But what if I need to make it clear to a non-specialist that their site is slow to load?
How can you provide persuasive evidence? In what form to issue, so that it is clear to the humanities.

Answer 1

https://gtmetrix.com/ Still handy.
Isn't it enough for the humanities that the main search engine tool evaluates their site as slow? )