---
lang: en
title: 'API docs: authentication.userservice'
keywords: LoopBack 4.0, LoopBack 4
sidebar: lb4_sidebar
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.

<b>Signature:</b>

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

## Methods

|  Method | Description |
|  --- | --- |
|  [convertToUserProfile(user)](./authentication.userservice.converttouserprofile.md) | Convert the user returned by <code>verifyCredentials()</code> to a common user profile that describes a user in your application |
|  [verifyCredentials(credentials)](./authentication.userservice.verifycredentials.md) | Verify the identity of a user, construct a corresponding user profile using the user information and return the user profile. |


