> ## Documentation Index
> Fetch the complete documentation index at: https://docs-dev-fix-docs-5546-update-db-search.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

> Describes common sign up and login errors that you might see when you authenticate users using Auth0 libraries.

# Common Auth0 Library Authentication Errors

The actions or input data of your users, during the sign up or the log in processes, might trigger errors. Here is a list of the most common errors that you might get if you use any of the Auth0 libraries for authentication.

## Sign up

In the case of a failed signup, the most common errors are:

| **Error**                           | **Description**                                                                                  |
| ----------------------------------- | ------------------------------------------------------------------------------------------------ |
| **invalid\_password**               | If the password used doesn't comply with the password policy for the connection                  |
| **invalid\_signup**                 | The user you are attempting to sign up is invalid                                                |
| **password\_dictionary\_error**     | The chosen password is too common                                                                |
| **password\_no\_user\_info\_error** | The chosen password is based on user information                                                 |
| **password\_strength\_error**       | The chosen [password is too weak](/docs/authenticate/database-connections/password-strength)     |
| **unauthorized**                    | If you cannot sign up for this application. May have to do with the violation of a specific rule |
| **user\_exists**                    | The user you are attempting to sign up has already signed up                                     |
| **username\_exists**                | The username you are attempting to sign up with is already in use                                |

## Log in

In the case of a failed login, the most common errors are:

| **Error**                       | **Description**                                                                                                                                                                                                                                                                                                                                 |
| ------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **access\_denied**              | When using web-based authentication, the resource server denies access per OAuth2 specifications                                                                                                                                                                                                                                                |
| **invalid\_user\_password**     | The username and/or password used for authentication are invalid                                                                                                                                                                                                                                                                                |
| **mfa\_invalid\_code**          | The <Tooltip tip="Multi-factor authentication (MFA): User authentication process that uses a factor in addition to username and password such as a code via SMS." cta="View Glossary" href="/docs/glossary?term=multi-factor+authentication+%28MFA%29">multi-factor authentication (MFA)</Tooltip> code provided by the user is invalid/expired |
| **mfa\_registration\_required** | The administrator has required [multi-factor authentication](/docs/secure/multi-factor-authentication), but the user has not enrolled                                                                                                                                                                                                           |
| **mfa\_required**               | The user must provide the [multi-factor authentication](/docs/secure/multi-factor-authentication) code to authenticate                                                                                                                                                                                                                          |
| **password\_leaked**            | If the password has been leaked and a different one needs to be used                                                                                                                                                                                                                                                                            |
| **PasswordHistoryError**        | The password provided for sign up/update has already been used (reported when [password history](/docs/authenticate/database-connections/password-options#password-history) feature is enabled)                                                                                                                                                 |
| **PasswordStrengthError**       | The password provided does not match the connection's [strength requirements](/docs/authenticate/database-connections/password-strength)                                                                                                                                                                                                        |
| **too\_many\_attempts**         | The account is blocked due to too many attempts to sign in                                                                                                                                                                                                                                                                                      |
| **unauthorized**                | The user you are attempting to sign in with is blocked                                                                                                                                                                                                                                                                                          |

## Learn more

* [Attack Protection](/docs/secure/attack-protection)