---
lang: en
title: 'API docs: authentication.userservice'
keywords: LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI
sidebar: lb4_sidebar
editurl: https://github.com/loopbackio/loopback-next/tree/master/packages/authentication
permalink: /doc/en/lb4/apidocs.authentication.userservice.html
---

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[Home](./index.md) &gt; [@loopback/authentication](./authentication.md) &gt; [UserService](./authentication.userservice.md)

## UserService interface

A service for performing the login action in an authentication strategy.

Usually a client user uses basic credentials to login, or is redirected to a third-party application that grants limited access.

Note: The creation of user is handled in the user controller by calling user repository APIs. For Basic auth, the user has to register first using some endpoint like `/register`<!-- -->. For 3rd-party auth, the user will be created if login is successful and the user doesn't exist in database yet.

Type `C` stands for the type of your credential object.

- For local strategy:

A typical credential would be: { username: username, password: password }

- For oauth strategy:

A typical credential would be: { clientId: string; clientSecret: string; callbackURL: string; }

It could be read from a local configuration file in the app

- For saml strategy:

A typical credential would be:

{ path: string; issuer: string; entryPoint: string; }

It could be read from a local configuration file in the app.

**Signature:**

```typescript
export interface UserService<U, C> 
```

## Methods

<table><thead><tr><th>

Method


</th><th>

Description


</th></tr></thead>
<tbody><tr><td markdown="1">

[convertToUserProfile(user)](./authentication.userservice.converttouserprofile.md)


</td><td markdown="1">

Convert the user returned by `verifyCredentials()` to a common user profile that describes a user in your application


</td></tr>
<tr><td markdown="1">

[verifyCredentials(credentials)](./authentication.userservice.verifycredentials.md)


</td><td markdown="1">

Verify the identity of a user, construct a corresponding user profile using the user information and return the user profile.


</td></tr>
</tbody></table>