Trust neither. The most optimal option I've found is webpagetest.org Its been quite handy lately. This tool does look interesting. Source: about 1 year ago

Webpagetest.org is another. Pagespeedinsights and lighthouse are great for identifying page load issues to fix, but actual page load times will always vary between the user and your web server. Universal analytics has some page load timings but that's going away soon and nothing afaik is in GA4. I've seen an example of building a page load timer in tag manager and dumping the results into an event. Source: about 1 year ago

So I am working on rebuilding our company's site with a new stack. I am running tests using webpagetest.org, and I am having trouble fully understanding the speed index results as well as the film strip view. The page renders quite fast everywhere I test it. Google Lighthouse shows it in the 90s + for performance score, however when I test the page on webpagetest, I get load times of 77 seconds (NOT MS) which is... Source: about 1 year ago

Webpagetest.org is great, and checking OP's site they have done an incredible job, I don't think I have ever made or seen an Ecom site this slick. Super clean waterfall view. Source: about 1 year ago

Thanks for the recommendation regarding webpagetest.org, another user made a similar recommendation so I will check it out. Source: over 1 year ago

An Android tablet and the CoolReader app. For me, it's simply the best eReader experience available. It's incredibly customisable. The only downside is it doesn't support PDF or AZW3, both of which can be reformatted to your preferred file type with Calibre anyway. Source: over 1 year ago

Cool reader is also another option https://sourceforge.net/projects/crengine/. Source: about 3 years ago