There are a number of things that can affect page load time:
images on the page
components on the page
data on the page
number of calls to the server
If you want to investigate your product speciifcally you might start with a proxy tool like fiddler that inspects everything sent/recieved over HTTP. A performance tool like JMeter will also display this information.
Identifying such issues is just one step towards rectifying them. One should be able to further analyze the factors from HAR files, PCAP files, Systrace for devices. Sometimes, there are repeated network calls when a connection is established. These can lead to chatty conversations. The best way to rectify such issues is to take the help of testing tools such as MOZARK Application Testing platform that helps you in identifying the real problem behind a slow page load time.
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