When should I prefer Server-side validation checks over Client-side validation checks

Question

Hi. Can someone tell me when I should prefer Server-side checks? I've been building web-applications for a few months now and I use client-side checks and I think that does the job. But I read somewhere that server-side checks increase security. Can someone explain how?

Answer 1

Yes, it is true that server-side checks increase security and the reason behind this is that the user can modify client-side data. Take an example of a web application that only does client-side checks. In this case, proxy interceptors can be used to capture the data after validation and these interceptors can be used to modify the requests and change the value to invalid values. If you rely only on client-side checks, there is a chance of the server receiving invalid inputs. But there are some cons of using server-side checks over client-side checks. It is suggested to use both the checks for max security.