Appwrite is an end-to-end backend server for Web, Mobile, Native, or Backend apps packaged as a set of Docker microservices. Appwrite abstracts the complexity and repetitiveness required to build a modern backend API from scratch and allows you to build secure apps faster.
Using Appwrite, you can easily integrate your app with user authentication and multiple sign-in methods, a database for storing and querying users and team data, storage and file management, image manipulation, Cloud Functions, and more services.
Auth0 is a service that abstracts how users authenticate to applications.
You can connect any application (written in any language or on any stack) to Auth0 and define its Connection, the method used to authenticate the users of that application:
Custom credentials: username + passwords
Social network logins: Google, Facebook, Twitter, and any OAuth2, OAuth1 or OpenID Connect provider
Enterprise directories: LDAP, Google Apps, Office 365, ADFS, AD, SAML-P, WS-Federation, etc.
Passwordless systems: TouchID, one time codes on SMS, or email