Authgear is an authentication server for web and mobile apps. It is written in Go and available as a Docker image. It runs on any container platform like Kuberentes. It is highly customizable yet comes with sensible defaults. It is built on top of OpenID Connect (OIDC) standard, making it very easy to integrate. It supports single sign-on (SSO) via integration with popular providers such as Google, Apple, and Azure Active Directory (AD). It also supports logging in via email address and phone number with one-time password or traditional password with strong password policy. Multiple factor authentication with time-based one-time password or out-out-band one-time password is available out of the box. Users can manage their sessions in the web-based settings page. Authgear, together with popular reverse proxies such as Nginx, can work as the authentication proxy for your other services.