How to make a website vulnerability scanner?

Question

Information Security

I want to write a service to scan a web site for vulnerabilities, something like detectify.com, The question is how exactly the scanning process takes place, for example SQL-injection or XSS
PS I just started reading on the topic of security, the project is purely for educational purposes

Answer 1

To do this, you need to understand what exactly the vulnerability is and how it works. Most likely, a dozen test servers will be needed, some will be obviously vulnerable. With different sets of vulnerabilities. And after you deal with them, then the experience will already be enough to write the service itself.
And for educational purposes, it is enough to write an example site (one-page), and a site that checks it (also one-page).