Calling public code from backend

Hello dear community,

I would like to perform some validity checks on the server side and client side.

I was asking myself if these checks are secure from client side manipulations.

What happens on server side, if the user manipulates the public sources on his device (client side)?

He could probably overcome some validity checks on the client side manipulating the public sources on his device. What about the code on the server side? Will it be manipulated as well?

The public code will not perform any sensible information of course.

Greetings

Norbert