[Vuejs]-Email only authentication with Vue.js and Vuex on Firebase

The provider you’re using is called the password provider. As its name implies it is heavily dependent on the user having (and knowing) a password. Since you are looking for passwordless authentication, I’d recommend against using the email+password provider as the basis.

Instead consider implementing a custom authentication provider. While this involves a few more components, it is not as difficult as you may think. You’ll need to run trusted code, which you can do either on a server you already have, or on Cloud Functions. In either of those cases, you’ll use one of the Admin SDKs to implement the sensitive parts of the authentication flow.

A quick list of steps that I think you’ll need:

1. Create an endpoint (e.g. a HTTP triggered Cloud Function) for the user to request an authentication email.
2. Implement the code for this endpoint to:
   1. Generate a random one-time code in there, which you’re going to send to the user. Firebase Authentication calls this the out-of-band (or OOB) code, since it’s sent to the user on a different medium than your app.
   2. Store this code and the user’s email address somewhere where only your server-side code can read it, e.g. in the Firebase Database or Cloud Firestore.
   3. Send an email to the user, with the code or a link to a page that includes the code and their email address.
3. Create an endpoint (e.g. again a HTTP function, or web page) where the user enters (e.g. by clicking on a link in the email) the OOB code and their email address.
4. Compare the code the user entered, to the one you stored before.
5. If the codes match, generate a custom token for the user and send it to them.
6. The user/app now signs into Firebase with the custom token.