Custom HTML

Hello,
I am using custom JS code to load a third part tool.
I see the script I use it getting loaded on client side.

If I integrate a supported third party tool, I see only the s.js is loaded.
I want to confirm with custom script, is the script loading is on client side unlike the third party tools like google analytics where the only loaded script is s.js.

For context I am trying to integrate with other analytics tools.