Thanks to its nearly endless customizability through plugins and themes, WordPress has come a long way from its roots as a blogging platform, today acting as the backbone for all kinds of web based applications from online stores to membership sites and e-book authoring platforms.
While traditionally only the site admins would log in to the WordPress dashboard, many of these new, application-like uses change that: when users need to be authenticated, the WordPress login is extended to visitors and customers.
WordPress provides good tools for managing user roles and capabilities, and they can be further extended with the help of plugins, but for a professional touch, that’s not quite enough — you also need to make sure the user experience fits that of your product as a whole. After all, seeing the default (or lightly styled) WordPress login screen when logging in to a web based application can leave an unfinished impression.
In this three-part tutorial series, I will show you how to fix this by customizing the login and new user registration functionality to fit your site’s looks, without violating WordPress’s best practices.
https://code.tutsplus.com/tutorials/build-a-custom-wordpress-user-flow-part-1-replace-the-login-page--cms-23627