> For the complete documentation index, see [llms.txt](https://fusionauth.io/docs/llms.txt)

# FusionAuth Documentation

Learn what FusionAuth is and how to get started using it.

FusionAuth is a Customer Identity and Access Management (CIAM) server that provides:

*   Authentication
*   Authorization
*   User Management

```mermaid
graph LR
    classDef orangeBorder stroke:#ff9800,stroke-width:2px;
    User((User)) -->|authenticates| FA(FusionAuth):::orangeBorder
    App[Application] -->|delegates auth| FA
    FA <-->|brokers identity| IdP[External IdPs]
    User -->|consumes| App
```

FusionAuth connects users, applications, and identity providers

FusionAuth provides a full implementation of [OAuth2](https://fusionauth.io/docs/lifecycle/authenticate-users/oauth.md), [OpenID Connect (OIDC)](https://fusionauth.io/docs/lifecycle/authenticate-users/identity-providers/overview-oidc.md), and [SAML v2](https://fusionauth.io/docs/lifecycle/authenticate-users/saml.md), where FusionAuth functions as both a [Service Provider (SP)](https://fusionauth.io/docs/lifecycle/authenticate-users/identity-providers/overview-samlv2.md) and a [SAML Identity Provider (IdP)](https://fusionauth.io/docs/lifecycle/authenticate-users/saml.md).

## Try

To get started with FusionAuth today, check out one of our [QuickStarts](https://fusionauth.io/docs/get-started/quickstarts.md).

[React React](https://fusionauth.io/docs/get-started/quickstarts/spa/react.md)

[Django Django](https://fusionauth.io/docs/get-started/quickstarts/web/quickstart-python-django-web.md)

[iOS iOS](https://fusionauth.io/docs/get-started/quickstarts/app/quickstart-swift-ios-native.md)

[Go Go](https://fusionauth.io/docs/get-started/quickstarts/api/quickstart-golang-api.md)

## Deploy

You can deploy FusionAuth anywhere: self-hosted on a [local machine](https://fusionauth.io/docs/get-started/download-and-install/docker.md), on-premises in [your own cloud](https://fusionauth.io/docs/cloud/marketplaces.md), on an [air-gapped server](https://fusionauth.io/docs/get-started/download-and-install/reference/air-gapping.md), or via a [managed FusionAuth Cloud instance](https://fusionauth.io/docs/cloud.md).

[Self-Host Self-Host](https://fusionauth.io/docs/get-started/download-and-install/docker.md)

[Cloud Marketplace Cloud Marketplace](https://fusionauth.io/docs/cloud/marketplaces.md)

[FusionAuth Cloud FusionAuth Cloud](https://fusionauth.io/pricing?step=plan&hosting=basic-cloud.md)

## Customization

FusionAuth is highly customizable, both in appearance and behavior. You can control every [page](https://fusionauth.io/docs/customize/look-and-feel/simple-theme-editor.md) and [message](https://fusionauth.io/docs/customize/email-and-messages/message-templates-replacement-variables.md). You can use lambda functions to customize [data validation](https://fusionauth.io/docs/extend/code/lambdas/login-validation.md), [MFA challenge logic](https://fusionauth.io/docs/extend/code/lambdas/mfa-requirement.md), [token transformation](https://fusionauth.io/docs/extend/code/lambdas/jwt-populate.md), and [much more](https://fusionauth.io/docs/extend/code/lambdas.md). You can use webhooks to [react to a wide variety of events](https://fusionauth.io/docs/extend/events-and-webhooks/events.md).

[Theme Theme](https://fusionauth.io/docs/customize/look-and-feel/simple-theme-editor.md)

[Messages Messages](https://fusionauth.io/docs/customize/email-and-messages/message-templates-replacement-variables.md)

[Lambdas Lambdas](https://fusionauth.io/docs/extend/code/lambdas.md)

## Authentication Protocols

FusionAuth supports most popular authentication protocols, including username/password, [a wide range of identity providers](https://fusionauth.io/docs/lifecycle/authenticate-users/identity-providers.md), [passkeys](https://fusionauth.io/docs/lifecycle/authenticate-users/passwordless/webauthn-passkeys.md), and [passwordless logic like magic links and OTP](https://fusionauth.io/docs/lifecycle/authenticate-users/passwordless.md).

[Identity Providers Identity Providers](https://fusionauth.io/docs/lifecycle/authenticate-users/identity-providers.md)

[Social Sign-On Social Sign-On](https://fusionauth.io/docs/lifecycle/authenticate-users/identity-providers.md#social-identity-providers)

[Enterprise Sign-On Enterprise Sign-On](https://fusionauth.io/docs/lifecycle/authenticate-users/identity-providers.md#enterprise-identity-providers)

[Passkeys Passkeys](https://fusionauth.io/docs/lifecycle/authenticate-users/passwordless/webauthn-passkeys.md)

[Passwordless Passwordless](https://fusionauth.io/docs/lifecycle/authenticate-users/passwordless.md)

## Authorization

Define permissions using role-based access control (RBAC) with [users](https://fusionauth.io/docs/get-started/core-concepts/users.md), [roles](https://fusionauth.io/docs/get-started/core-concepts/roles.md), [groups](https://fusionauth.io/docs/get-started/core-concepts/groups.md), [applications](https://fusionauth.io/docs/get-started/core-concepts/applications.md), and [entities](https://fusionauth.io/docs/get-started/core-concepts/entity-management.md). For highly granular permissions, check out our [fine-grained authorization](https://fusionauth.io/docs/extend/fine-grained-authorization.md) integration.

[Role-Based Access Control (RBAC) Role-Based Access Control (RBAC)](https://fusionauth.io/docs/get-started/core-concepts/roles.md)

[Fine-Grained Authorization (FGA) Fine-Grained Authorization (FGA)](https://fusionauth.io/docs/extend/fine-grained-authorization.md)

## Security

Configure threat mitigation and detection features like [multi-factor authentication (MFA)](https://fusionauth.io/docs/lifecycle/authenticate-users/multi-factor-authentication.md), [breached password detection](https://fusionauth.io/docs/operate/secure/breached-password-detection.md), [rate limiting](https://fusionauth.io/docs/operate/secure/advanced-threat-detection.md#customizable-rate-limiting), and [captcha](https://fusionauth.io/docs/operate/secure/advanced-threat-detection.md#captcha) to keep both you and your users secure.

[Multi-Factor Authentication (MFA) Multi-Factor Authentication (MFA)](https://fusionauth.io/docs/lifecycle/authenticate-users/multi-factor-authentication.md)

[Captcha Captcha](https://fusionauth.io/docs/operate/secure/advanced-threat-detection.md#captcha)

[Rate Limiting Rate Limiting](https://fusionauth.io/docs/operate/secure/advanced-threat-detection.md#customizable-rate-limiting)

## Support

When you can't figure out how to solve a problem yourself, FusionAuth provides [first-class support](https://fusionauth.io/docs/operate/troubleshooting/technical-support.md) from battle-hardened humans.