What are some alternatives?
When comparing Preact.js and React, you can also consider the following products
Vue.js - Reactive Components for Modern Web Interfaces
Okta - Enterprise-grade identity management for all your apps, users & devices
OneLogin - On-demand SSO, directory integration, user provisioning and more
Deku - Functional view library for building UI components as an alternative to React
Atlassian Crowd - Crowd is a single sign-on and user identity solution.