User blog hosting “Habrahabr” has published a small investigation as to why the web email service from Google Gmail so slow loading.
When using the built-in In Google Chrome Devtools tool Lighthouse you may find that Gmail gives performance at the level of 2 out of 100.
As it turned out, the reasons for this slowness can be summarized as follows. In the code there are pieces that provide compatibility with older browsers, not all of them are necessary in the modern world. There are too heavy tools for various additional tasks of the service. Minor elements are loaded on the page initially. So, a widget Hangouts prevents major resources Gmail. In addition, Google somehow does not use its product in some of its technologies, which it actively promotes in their conferences.