How to make a general authorization for a grid of sites?

Question

JSON Web Token

There is a grid of 10 sites. It would be desirable to make transparent uniform authorization between them. Those. if a user is registered on one site, when he enters another site of this network, he is automatically registered. How to do it?
For example, now I'm trying to make an external authorization server. And now the authorization request goes not to mydomen.com/authbut to authserver.com. I'm trying to put a cookie - it is not set. How do other services get around this? How is it generally implemented?

Answer 1

Cross-Site Authorization

Answer 2

This is called Single Sign-on. It is implemented by introducing a separate authentication service that works according to one of the popular protocols: OAuth2, OpenId, SAML. There are ready-made solutions and services like Auth0, and there are those that are fashionable to deploy on your own: Keycloak, WSO2, Identity Server 4, ...
It is fashionable to write it yourself - it will be long, expensive, important