Long thought to be the only way to authenticate users online, email is an old technology that is not necessarily suited for every authentication needs. Julia Enthoven, a video startup co-founder at Kapwing, recently made the case against email sign in. In her blog, she argues that in many cases, app makers should refrain from using email as an authentication method and instead rely on OAuth. It should be noted that "sign in" refers to user registration and authentication in the context of an application -- not to the typical email subscription process.
What is OAuth? OAuth refers to an authentication method that relies on an external, established service to manage permissions for an application's user. For example, a subscription-based SaaS can use Google to authenticate and manage its users.
This delegated process allows OAuth users to consume the service through a centralized interface. They can manage their account and the permissions they have granted to external applications from a single place. From a user's perspective, OAuth makes transactions easier to track and provides a higher level of security. There's less hassle involved in registering and authenticating, and less back-and-forth between email and apps during the registration process.
From a SaaS provider's perspective, there are numerous advantages to using delegated OAuth, the least of which is that it makes shared accounts -- where multiple people use the same subscription through a shared email in order to avoid fees. As the author says, it's pretty obvious:
Don’t underestimate the engineering effort that goes into a robust identity system. If you’re just getting started, email sign in shouldn’t be in the MVP.