FirebaseUI for Web — Auth

FirebaseUI is an open-source JavaScript library for Web that provides simple,
customizable UI bindings on top of Firebase SDKs
to eliminate boilerplate code and promote best practices.

FirebaseUI Auth provides a drop-in auth solution that handles the UI flows for
signing in users with email addresses and passwords, phone numbers, Identity
Provider Sign In including Google, Facebook, GitHub, Twitter, Apple, Microsoft,
Yahoo, OpenID Connect (OIDC) providers and SAML providers. It is built on top of
Firebase Auth.

The FirebaseUI component implements best practices for authentication on mobile
devices and websites, helping to sign-in and sign-up conversion for your app. It
also handles cases like account recovery and account linking that can be
security sensitive and error-prone to handle.

FirebaseUI Auth clients are also available for
iOS and
Android.

FirebaseUI fully supports all recent browsers. Signing in with federated
providers (Google, Facebook, Twitter, GitHub, Apple, Microsoft, Yahoo, OIDC,
SAML) is also supported in Cordova/Ionic environments. Additional non-browser
environments(React Native...) or Chrome extensions will be added once the
underlying Firebase core SDK supports them in a way that is compatible with
FirebaseUI.

Table of Contents

1. Demo
2. Installation
3. Usage instructions
4. Configuration
5. Customization
6. Advanced
7. Developer Setup
8. IAP External Identities Support with FirebaseUI
9. Cordova Setup
10. React DOM Setup
11. Angular Setup
12. Known issues
13. Deprecated APIs
14. Release Notes

Demo

Accessible here:
https://fir-ui-demo-84a6c.firebaseapp.com.

Installation

$3

You just need to include the following script and CSS file in the tag
of your page, below the initialization snippet from the Firebase Console:

``html


`

#### Localized Widget

Localized versions of the widget are available through the CDN. To use a
localized widget, load the localized JS library instead of the default library:

`html


`

where {LANGUAGE_CODE} is replaced by the code of the language you want. For example, the French
version of the library is available at
https://www.gstatic.com/firebasejs/ui/6.0.2/firebase-ui-auth__fr.js. The list of available
languages and their respective language codes can be found at LANGUAGES.md.

Right-to-left languages also require the right-to-left version of the stylesheet, available at
https://www.gstatic.com/firebasejs/ui/6.0.2/firebase-ui-auth-rtl.css, instead of the default
stylesheet. The supported right-to-left languages are Arabic (ar), Farsi (fa), and Hebrew (iw).

$3

Install FirebaseUI and its peer-dependency Firebase via npm using the following
commands:

`bash
$ npm install firebase firebaseui --save
`

You can then import the following modules within your source files:

`javascript
import firebase from 'firebase/compat/app';
import * as firebaseui from 'firebaseui'
import 'firebaseui/dist/firebaseui.css'
`

$3

Install FirebaseUI and its dependencies via Bower using the following command:

`bash
$ bower install firebaseui --save
`

You can then include the required files in your HTML, if your HTTP Server serves
the files within bower_components/:

`html


`

Using FirebaseUI for Authentication

FirebaseUI includes the following flows:

1. Interaction with Identity Providers such as Google and Facebook
2. Phone number based authentication
3. Sign-up and sign-in with email accounts (email/password and email link)
4. Password reset
5. Prevention of account duplication (activated when
"One account per email address" setting is enabled in the
Firebase console. This setting is enabled
by default.)
6. Integration with
one-tap sign-up
7. Ability to upgrade anonymous users through sign-in/sign-up.
8. Sign-in as a guest

$3

To use FirebaseUI to authenticate users you first need to configure each
provider you want to use in their own developer app settings. Please read the
Before you begin section of Firebase Authentication at the following links:

- Phone number
- Email and password
- Google
- Facebook
- Twitter
- Github
- Anonymous
- Email link
- Apple
- Microsoft
- Yahoo

For Google Cloud's Identity Platform (GCIP)
developers, you can also enable SAML and OIDC providers following the
instructions:

- SAML
- OIDC

$3

You first need to initialize your
Firebase app. The
firebase.auth.Auth instance should be passed to the constructor of
firebaseui.auth.AuthUI. You can then call the start method with the CSS
selector that determines where to create the widget, and a configuration object.

The following example shows how to set up a sign-in screen with all supported
providers. Please refer to the demo application in the examples folder
for a more in-depth example, showcasing a Single Page Application mode.

> Firebase and FirebaseUI do not work when executed directly from a file (i.e.
> opening the file in your browser, not through a web server). Always run
> firebase serve (or your preferred local server) to test your app locally.

`html
















Welcome to My Awesome App

When redirecting back from Identity Providers like Google
and Facebook or email link sign-in, start() method needs to be called to
finish the sign-in flow.
If it requires a user interaction to start the initial sign-in process, you need
to check if there is a pending redirect operation going on on page load to check
whether start() needs to be called.

To check if there is a pending redirect operation to complete a sign-in attempt,
check isPendingRedirect() before deciding whether to render FirebaseUI
via start().

`javascript
if (ui.isPendingRedirect()) {
ui.start('#firebaseui-auth-container', uiConfig);
}
`

Here is how you would track the Auth state across all your pages:

`html













Welcome to My Awesome App

`

Configuration

FirebaseUI supports the following configuration parameters.

$3

The role of a credential helper is to help your users sign into your website.
When one is enabled, your users will be prompted with email addresses and
usernames they have saved from your app or other applications.
FirebaseUI supports the one-tap sign-up credential helper. accountchooser.com
is no longer supported.

#### One-tap sign-up

One-tap sign-up
provides seamless authentication flows to
your users with Google's one tap sign-up and automatic sign-in APIs.
With one tap sign-up, users are prompted to create an account with a dialog
that's inline with FirebaseUI NASCAR screen. With just one tap, they get a
secure, token-based, passwordless account with your service, protected by their
Google Account. As the process is frictionless, users are much more likely to
register.
Returning users are signed in automatically, even when they switch devices or
platforms, or after their session expires.
One-tap sign-up integrates with FirebaseUI and if you request Google OAuth
scopes, you will still get back the expected Google OAuth access token even if
the user goes through the one-tap flow. However, in that case 'redirect' flow is
always used even when 'popup' is specified.
In addition, if you choose to force prompt for Google sign-in, one-tap auto
sign-in will be automatically disabled.
One-tap is an additive feature and is only supported in the latest evergreen
modern browser environments.
For more information on how to configure one-tap sign-up, refer to the
one-tap get started guide.

The following example shows how to configure one-tap sign-up with FirebaseUI.
Along with the corresponding one-tap credentialHelper, the Google OAuth
clientId has to be provided with the Firebase Google provider:

`javascript
ui.start('#firebaseui-auth-container', {
signInOptions: [
{
// Google provider must be enabled in Firebase Console to support one-tap
// sign-up.
provider: firebase.auth.GoogleAuthProvider.PROVIDER_ID,
// Required to enable ID token credentials for this provider.
// This can be obtained from the Credentials page of the Google APIs
// console. Use the same OAuth client ID used for the Google provider
// configured with GCIP or Firebase Auth.
clientId: 'xxxxxxxxxxxxxxxxx.apps.googleusercontent.com'
},
firebase.auth.FacebookAuthProvider.PROVIDER_ID,
firebase.auth.TwitterAuthProvider.PROVIDER_ID,
firebase.auth.GithubAuthProvider.PROVIDER_ID,
firebase.auth.EmailAuthProvider.PROVIDER_ID,
],
// Required to enable one-tap sign-up credential helper.
credentialHelper: firebaseui.auth.CredentialHelper.GOOGLE_YOLO
});
// Auto sign-in for returning users is enabled by default except when prompt is
// not 'none' in the Google provider custom parameters. To manually disable:
ui.disableAutoSignIn();
`

Auto sign-in for returning users can be disabled by calling
ui.disableAutoSignIn(). This may be needed if the FirebaseUI sign-in page is
being rendered after the user signs out.

To see FirebaseUI in action with one-tap sign-up, check out the FirebaseUI
demo app.

|Credential Helper |Value |
|----------------------------------|------------------------------------------------------|
|One-tap sign-up |firebaseui.auth.CredentialHelper.GOOGLE_YOLO |
|None (disable) |firebaseui.auth.CredentialHelper.NONE |

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|Provider |Value |
|------------------|------------------------------------------------|
|Google |firebase.auth.GoogleAuthProvider.PROVIDER_ID |
|Facebook |firebase.auth.FacebookAuthProvider.PROVIDER_ID|
|Twitter |firebase.auth.TwitterAuthProvider.PROVIDER_ID |
|Github |firebase.auth.GithubAuthProvider.PROVIDER_ID |
|Email and password|firebase.auth.EmailAuthProvider.PROVIDER_ID |
|Phone number |firebase.auth.PhoneAuthProvider.PROVIDER_ID |
|Anonymous |firebaseui.auth.AnonymousAuthProvider.PROVIDER_ID|
|Apple |apple.com |
|Microsoft |microsoft.com |
|Yahoo |yahoo.com |
|SAML (GCIP only) |saml.* |
|OIDC (GCIP only) |oidc.* |

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To specify custom scopes, or custom OAuth parameters per provider, you can pass
an object instead of just the provider value:

`javascript
ui.start('#firebaseui-auth-container', {
signInOptions: [
{
provider: firebase.auth.GoogleAuthProvider.PROVIDER_ID,
scopes: [
'https://www.googleapis.com/auth/contacts.readonly'
],
customParameters: {
// Forces account selection even when one account
// is available.
prompt: 'select_account'
}
},
{
provider: firebase.auth.FacebookAuthProvider.PROVIDER_ID,
scopes: [
'public_profile',
'email',
'user_likes',
'user_friends'
],
customParameters: {
// Forces password re-entry.
auth_type: 'reauthenticate'
}
},
// Twitter does not support scopes.
firebase.auth.TwitterAuthProvider.PROVIDER_ID,
// Other providers don't need to be given as object.
firebase.auth.EmailAuthProvider.PROVIDER_ID
]
});
`

#### Generic OAuth provider

You can let your users authenticate with FirebaseUI using OAuth providers like
Apple,
Microsoft Azure Active Directory
and Yahoo
by integrating generic OAuth Login into your app.

You just need to pass the provider ID in signInOptions, FirebaseUI provides
the default configurations for the sign in button(button color, icon and display
name):

`javascript
ui.start('#firebaseui-auth-container', {
signInOptions: [
'apple.com',
'microsoft.com',
'yahoo.com',
]
});
`

You can also override these default configurations with your own custom ones.
Generic OAuth providers' signInOptions support the following configuration
parameters.

`javascript
ui.start('#firebaseui-auth-container', {
signInOptions: [
{
provider: 'microsoft.com',
providerName: 'Microsoft',
// To override the full label of the button.
// fullLabel: 'Login with Microsoft',
buttonColor: '#2F2F2F',
iconUrl: '',
loginHintKey: 'login_hint',
scopes: [
'mail.read'
],
customParameters: {
prompt: 'consent'
}
}
]
});
`

$3

For GCIP customers, you can enable your
app for
OpenID Connect (OIDC)
authentication with FirebaseUI.

OIDC providers' signInOptions support the following configuration parameters.

`javascript
ui.start('#firebaseui-auth-container', {
signInOptions: [
{
provider: 'oidc.myProvider',
providerName: 'MyOIDCProvider',
// To override the full label of the button.
// fullLabel: 'Employee Login',
buttonColor: '#2F2F2F',
iconUrl: '',
customParameters: {
OIDCSupportedParameter: 'value'
}
}
]
});
`

$3

For GCIP customers, you can enable your
app for
SAML
authentication with FirebaseUI.

SAML providers' signInOptions support the following configuration parameters.

`javascript
ui.start('#firebaseui-auth-container', {
signInOptions: [
{
provider: 'saml.myProvider',
providerName: 'MySAMLProvider',
// To override the full label of the button.
// fullLabel: 'Constractor Portal',
buttonColor: '#2F2F2F',
iconUrl: ''
}
]
});
`

$3

You can configure either email/password or email/link sign-in with FirebaseUI by
providing the relevant object in the configuration signInOptions
array.

You can disable new user sign up with email providers by setting the flag
disableSignUp.status to true. This will display an error message when new
users attempt to sign up.

Note that this flag will only disable sign up from the UI and will not prevent
sign up via REST API. It is highly recommended that Identity Platform projects
enforce this policy via one of these 2 mechanisms:

- Blocking functions: Set a beforeCreate trigger to disable sign up for email
providers.
- In the Cloud Console / Settings / USERS tab, uncheck Enable create (sign-up)
checkbox. Though for this setting, sign up for all providers will be disabled.

#### Email and Password

Email and password authentication is the default sign-in method for Email
providers.
The EmailAuthProvider with email and password can be configured to require the
user to enter a display name (defaults to true).

`javascript
ui.start('#firebaseui-auth-container', {
signInOptions: [
{
provider: firebase.auth.EmailAuthProvider.PROVIDER_ID,
requireDisplayName: false
}
]
});
`

#### Email Link Authentication

FirebaseUI supports sign-in and sign-up with email links.
Using email link sign-in with FirebaseUI comes with the following benefits:

- End to end support for email link sign-in with only a few configuration lines.
- Enforces security and privacy best practices.
- Ability to force same device flows or allow cross device flows where a user
can start the flow on one device and end it on another. This also covers
Android where email link sign-in is also supported with
FirebaseUI-android and
FirebaseUI-ios
for iOS support.
- Ability to switch to email link sign-in while continuing to sign-in existing
users with email and password.
- Ability to support account linking, where an existing email link user signing
in with Facebook for the first time using the same email will have
both accounts merged so they can sign in with either (Facebook or email link)
going forward.
- Ability to support anonymous user upgrade as long as the flow starts and ends
on the same device. Users opening the link on a different device will be
notified to open the link on the same device where the flow started.


The sample code below demonstrates how to configure email link sign-in with
FirebaseUI. In this example, cross device flows are allowed and additional state
is passed in the URL, as well as the ability to configure the link to open via
mobile application too.

`javascript
ui.start('#firebaseui-auth-container', {
signInOptions: [
{
provider: firebase.auth.EmailAuthProvider.PROVIDER_ID,
// Use email link authentication and do not require password.
// Note this setting affects new users only.
// For pre-existing users, they will still be prompted to provide their
// passwords on sign-in.
signInMethod: firebase.auth.EmailAuthProvider.EMAIL_LINK_SIGN_IN_METHOD,
// Allow the user the ability to complete sign-in cross device, including
// the mobile apps specified in the ActionCodeSettings object below.
forceSameDevice: false,
// Used to define the optional firebase.auth.ActionCodeSettings if
// additional state needs to be passed along request and whether to open
// the link in a mobile app if it is installed.
emailLinkSignIn: function() {
return {
// Additional state showPromo=1234 can be retrieved from URL on
// sign-in completion in signInSuccess callback by checking
// window.location.href.
// If you are using a fragment in the URL, additional FirebaseUI
// parameters will be appended to the query string component instead
// of the fragment.
// So for a url: https://www.example.com/#/signin
// The completion URL will take the form:
// https://www.example.com/?uid_sid=xyz&ui_sd=0#/signin
// This should be taken into account when using frameworks with "hash
// routing".
url: 'https://www.example.com/completeSignIn?showPromo=1234',
// Custom FDL domain.
dynamicLinkDomain: 'example.page.link',
// Always true for email link sign-in.
handleCodeInApp: true,
// Whether to handle link in iOS app if installed.
iOS: {
bundleId: 'com.example.ios'
},
// Whether to handle link in Android app if opened in an Android
// device.
android: {
packageName: 'com.example.android',
installApp: true,
minimumVersion: '12'
}
};
}
}
]
});
`

When rendering the sign-in UI conditionally (relevant for single page apps),
use ui.isPendingRedirect() to detect if the URL corresponds to a sign-in with
email link and the UI needs to be rendered to complete sign-in.
You can also just use
firebase.auth().isSignInWithEmailLink(window.location.href).

`javascript
// Is there an email link sign-in?
if (ui.isPendingRedirect()) {
ui.start('#firebaseui-auth-container', uiConfig);
}
// This can also be done via:
if (firebase.auth().isSignInWithEmailLink(window.location.href)) {
ui.start('#firebaseui-auth-container', uiConfig);
}
`

Additional state passed in the url can be retrieved on sign-in
completion via the signInSuccess callbacks.

If you are using a fragment in the URL, additional FirebaseUI parameters will be
appended to the query string component instead of the fragment.
So for a url https://www.example.com/#/signin, the completion URL will take
the form https://www.example.com/?uid_sid=xyz&ui_sd=0#/signin.
This should be taken into account when using frameworks with "hash routing".

`javascript
// ...
signInSuccessWithAuthResult: function(authResult, redirectUrl) {
// If a user signed in with email link, ?showPromo=1234 can be obtained from
// window.location.href.
// ...
return false;
}
`

FirebaseUI uses the
history API to
clear the URL from query parameters related to email link sign-in after the
one-time code is processed. This prevents the user from re-triggering the
sign-in completion flow again on page reload or if the user signs out and tries
to sign in again in a single page application, etc.

When same device flows are not enforced, a user going through account linking
flow (eg. user signing in with Facebook with an email that belongs to an
existing email link user) opening the link on a different device would be given
the choice to continue sign-in with email link without merging the Facebook
credential or instructed to open the link on the same device where the flow was
initiated to successfully merge both accounts.

You cannot use email/password and email/link sign-in at the same time. Only one
mode can be configured at a time. However, if you previously signed up users
with passwords. Switching to email/link will only apply to new users and
existing password users will continue to be prompted for password on sign-in.

$3

The PhoneAuthProvider can be configured with custom reCAPTCHA parameters
whether reCAPTCHA is visible or invisible (defaults to normal). Refer to the
reCAPTCHA API docs for
more details.

The default country to select in the phone number input can also be set.
List of supported country codes. If unspecified,
the phone number input will default to the United States (+1).

The countries to select can also be configured with blacklistedCountries or
whitelistedCountries. It accepts either ISO (alpha-2) or E164
(prefix with '+') formatted country code. Invalid country code will be ignored.
whitelistedCountries and blacklistedCountries cannot be specified at the
same time.

The following options are currently supported. Any other
parameters will be ignored.

`javascript
ui.start('#firebaseui-auth-container', {
signInOptions: [
{
provider: firebase.auth.PhoneAuthProvider.PROVIDER_ID,
recaptchaParameters: {
type: 'image', // 'audio'
size: 'normal', // 'invisible' or 'compact'
badge: 'bottomleft' //' bottomright' or 'inline' applies to invisible.
},
defaultCountry: 'GB', // Set default country to the United Kingdom (+44).
// For prefilling the national number, set defaultNationNumber.
// This will only be observed if only phone Auth provider is used since
// for multiple providers, the NASCAR screen will always render first
// with a 'sign in with phone number' button.
defaultNationalNumber: '1234567890',
// You can also pass the full phone number string instead of the
// 'defaultCountry' and 'defaultNationalNumber'. However, in this case,
// the first country ID that matches the country code will be used to
// populate the country selector. So for countries that share the same
// country code, the selected country may not be the expected one.
// In that case, pass the 'defaultCountry' instead to ensure the exact
// country is selected. The 'defaultCountry' and 'defaultNationaNumber'
// will always have higher priority than 'loginHint' which will be ignored
// in their favor. In this case, the default country will be 'GB' even
// though 'loginHint' specified the country code as '+1'.
loginHint: '+11234567890',
// You can provide a 'whitelistedCountries' or 'blacklistedCountries' for
// countries to select. It takes an array of either ISO (alpha-2) or
// E164 (prefix with '+') formatted country codes. If 'defaultCountry' is
// not whitelisted or is blacklisted, the default country will be set to
// the first country available (alphabetical order). Notice that
// 'whitelistedCountries' and 'blacklistedCountries' cannot be specified
// at the same time.
whitelistedCountries: ['US', '+44']
}
]
});
`

$3

The AnonymousAuthProvider can be enabled to let users continue as a guest. If
a user is already signed in anonymously, clicking this sign-in option will keep
the same current anonymous user. In addition, when auto-upgrade for anonymous
users is enabled in addition to this option and a user is already signed in
anonymously, clicking this sign-in option will also keep the same current
anonymous user.

`javascript
ui.start('#firebaseui-auth-container', {
signInOptions: [
{
provider: firebaseui.auth.AnonymousAuthProvider.PROVIDER_ID
}
]
});
`

$3

Two sign in flows are available:

- redirect, the default, will perform a full page redirect to the sign-in page
of the provider (Google, Facebook...). This is recommended for mobile apps.
- The popup flow will open a popup to the sign-in page of the provider. If the
popup is blocked by the browser, it will fall back to a full page redirect.

$3

#### signInSuccessWithAuthResult(authResult, redirectUrl)

The signInSuccessWithAuthResult callback is invoked when user signs in
successfully.
The authResult provided here is a firebaseui.auth.AuthResult object, which
includes the current logged in user, the credential used to sign in the user,
additional user info indicating if the user is new or existing and operation
type like 'signIn' or 'link'. This callback will replace signInSuccess in
future.

Parameters:

|Name |Type | Optional|Description |
|-------------|------------------------------|---------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|authResult|firebaseui.auth.AuthResult |No |The AuthResult of successful sign-in operation. The AuthResult object has same signature as firebase.auth.UserCredential.|
|redirectUrl|string |Yes |The URL where the user is redirected after the callback finishes. It will only be given if you overwrite the sign-in success URL.|

Should return: boolean

If the callback returns true, then the page is automatically redirected
depending on the case:

- If no signInSuccessUrl parameter was given in the URL (See:
Overwriting the sign-in success URL)
then the default signInSuccessUrl in config is used.
- If the value is provided in the URL, that value will be used instead of the
static signInSuccessUrl in config.

If the callback returns false or nothing, the page is not automatically
redirected.

#### signInSuccess(currentUser, credential, redirectUrl)

This callback will be deprecated and will be replaced by
signInSuccessWithAuthResult which takes firebaseui.auth.AuthResult.

Parameters:

|Name |Type | Optional|Description |
|-------------|------------------------------|---------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|currentUser|firebase.User |No |The logged in user. |
|credential |firebase.auth.AuthCredential|Yes |The credential used to sign in the user. |
|redirectUrl|string |Yes |The URL where the user is redirected after the callback finishes. It will only be given if you overwrite the sign-in success URL.|

Should return: boolean

If the callback returns true, then the page is automatically redirected
depending on the case:

- If no signInSuccessUrl parameter was given in the URL (See:
Overwriting the sign-in success URL)
then the default signInSuccessUrl in config is used.
- If the value is provided in the URL, that value will be used instead of the
static signInSuccessUrl in config.

If the callback returns false or nothing, the page is not automatically
redirected.

#### signInFailure(error)

The signInFailure callback is provided to handle any unrecoverable error
encountered during the sign-in process.
The error provided here is a firebaseui.auth.AuthUIError error with the
following properties.

firebaseui.auth.AuthUIError properties:

|Name |Type |Optional |Description |
|---------|----------------|---------|-----------------------|
|code |string |No |The corresponding error code. Currently the only error code supported is firebaseui/anonymous-upgrade-merge-conflict |
|credential |firebase.auth.AuthCredential|Yes |The existing non-anonymous user credential the user tried to sign in with.|

Should return: Promise|void

FirebaseUI will wait for the returned promise to handle the reported error
before clearing the UI. If no promise is returned, the UI will be cleared on
completion. Even when this callback resolves, signInSuccessWithAuthResult
callback will not be triggered.

This callback is required when autoUpgradeAnonymousUsers is enabled.

#### uiShown()

This callback is triggered the first time the widget UI is rendered. This is
useful for cases where the application should display a custom loader before
FirebaseUI is displayed.

$3

`html
















Welcome to My Awesome App

To support this behavior, FirebaseUI makes it easy to "upgrade" an anonymous
account to a permanent account. To do so, simply set autoUpgradeAnonymousUsers
to true when you configure the sign-in UI (this option is disabled by
default).

FirebaseUI links the new credential with the anonymous account using Firebase
Auth's linkWithCredential method:
`javascript
anonymousUser.linkWithCredential(permanentCredential);
`
The user will retain the same uid at the end of the flow and all data keyed
on that identifier would still be associated with that same user.

Anonymous user upgrade is also supported by email link sign-in in FirebaseUI.
An anonymous user triggering the email link option will, on return from clicking
the link, upgrade to an email link user.
However, forceSameDevice must be set to true in the email signInOption.
This is to ensure that when the user clicks the link, it is opened on the same
device/browser where the initial anonymous user exists.

#### Handling anonymous user upgrade merge conflicts

There are cases when a user, initially signed in anonymously, tries to
upgrade to an existing Firebase user. For example, a user may have signed up
with a Google credential on another device. When trying to upgrade to the
existing Google user, an error auth/credential-already-in-use will be thrown
by Firebase Auth as an existing user cannot be linked to another existing user.
No two users can share the same credential. In that case, both user data
have to be merged before one user is discarded (typically the anonymous user).
In the case above, the anonymous user shopping cart will be copied locally,
the anonymous user will be deleted and then the user is signed in with the
permanent credential. The anonymous user data in temporary storage will be
copied back to the non-anonymous user.

FirebaseUI will trigger the signInFailure callback with an error code
firebaseui/anonymous-upgrade-merge-conflict when the above occurs. The error
object will also contain the permanent credential.
Sign-in with the permanent credential should be triggered in the callback to
complete sign-in.
Before sign-in can be completed via
auth.signInWithCredential(error.credential), the data of the anonymous user
must be copied and the anonymous user deleted. After sign-in completion, the
data has to be copied back to the non-anonymous user. An example below
illustrates how this flow would work if user data is persisted using Firebase
Realtime Database.

Example:

`javascript
// Temp variable to hold the anonymous user data if needed.
var data = null;
// Hold a reference to the anonymous current user.
var anonymousUser = firebase.auth().currentUser;
ui.start('#firebaseui-auth-container', {
// Whether to upgrade anonymous users should be explicitly provided.
// The user must already be signed in anonymously before FirebaseUI is
// rendered.
autoUpgradeAnonymousUsers: true,
signInSuccessUrl: '',
signInOptions: [
firebase.auth.GoogleAuthProvider.PROVIDER_ID,
firebase.auth.FacebookAuthProvider.PROVIDER_ID,
firebase.auth.EmailAuthProvider.PROVIDER_ID,
firebase.auth.PhoneAuthProvider.PROVIDER_ID
],
callbacks: {
signInSuccessWithAuthResult: function(authResult, redirectUrl) {
// Process result. This will not trigger on merge conflicts.
// On success redirect to signInSuccessUrl.
return true;
},
// signInFailure callback must be provided to handle merge conflicts which
// occur when an existing credential is linked to an anonymous user.
signInFailure: function(error) {
// For merge conflicts, the error.code will be
// 'firebaseui/anonymous-upgrade-merge-conflict'.
if (error.code != 'firebaseui/anonymous-upgrade-merge-conflict') {
return Promise.resolve();
}
// The credential the user tried to sign in with.
var cred = error.credential;
// If using Firebase Realtime Database. The anonymous user data has to be
// copied to the non-anonymous user.
var app = firebase.app();
// Save anonymous user data first.
return app.database().ref('users/' + firebase.auth().currentUser.uid)
.once('value')
.then(function(snapshot) {
data = snapshot.val();
// This will trigger onAuthStateChanged listener which
// could trigger a redirect to another page.
// Ensure the upgrade flow is not interrupted by that callback
// and that this is given enough time to complete before
// redirection.
return firebase.auth().signInWithCredential(cred);
})
.then(function(user) {
// Original Anonymous Auth instance now has the new user.
return app.database().ref('users/' + user.uid).set(data);
})
.then(function() {
// Delete anonymnous user.
return anonymousUser.delete();
}).then(function() {
// Clear data in case a new user signs in, and the state change
// triggers.
data = null;
// FirebaseUI will reset and the UI cleared when this promise
// resolves.
// signInSuccessWithAuthResult will not run. Successful sign-in
// logic has to be run explicitly.
window.location.assign('');
});

}
}
});
`

$3

For GCIP customers, you can build
a tenant-specific sign-in page with FirebaseUI. Make sure you've enabled
multi-tenancy for your project and configured your tenants. See the
Multi-tenancy quickstart
to learn how.

This feature requires firebase
version 6.6.0 or higher.


To use FirebaseUI with multi-tenancy, you need to set the tenant ID on the
Auth instance being passed to FirebaseUI before calling ui.start().

`javascript
// The Firebase Auth instance.
var auth = firebase.auth();
// Initialize FirebaseUI.
var ui = new firebaseui.auth.AuthUI(auth);
// Set the tenant ID on Auth instance.
auth.tenantId = selectedTenantId;
// Start the sign-in flow in selected tenant.
// All sign-in attempts will now use this tenant ID.
ui.start('#firebaseui-auth-container', selectedTenantConfig);
`

FirebaseUI only handles the sign-in flows for you, you will still need to build
your own UI to let the end users select a tenant to sign in with.
You can refer to the example in this
guide.

There is also a
quickstart
app available to demonstrate how to build a single sign-in page with the
FirebaseUI for two tenants which have different sets of identity providers
enabled.

Customizing FirebaseUI for authentication

Currently, FirebaseUI does not offer customization out of the box. However, the
HTML around the widget is not affected by it so you can display everything you
want around the widget container.

Advanced

$3

Upon initialization, FirebaseUI will look for the mode parameter in the URL.
Depending on the value of this parameter, it will trigger a specific mode. When
no mode parameter is found, it will default to the sign-in mode.

You can change the name of this parameter with the queryParameterForWidgetMode
configuration parameter.

|Query parameter value|Description |
|---------------------|------------|
|?mode=select |Sign-in mode|

Example:

https://?mode=select

$3

You can pass a query parameter to the widget's URL that will overwrite the URL
the user is redirected to after a successful sign-in. If you do so, you must set
the configuration signInSuccessUrl value (even if it will be overwritten).
When passing the redirect URL this way, the signInSuccessWithAuthResult
callback will receive the value as the redirectUrl argument.

You must include the mode explicitly in the URL when using the
signInSuccessUrl parameter, otherwise FirebaseUI will directly redirect to the
URL specified.

You can change the name of this parameter with the
queryParameterForSignInSuccessUrl configuration parameter.

Example:

https://?mode=select&signInSuccessUrl=signedIn.html will
redirect the user to https:///signedIn.html after a
successful sign-in flow.

Developer Setup

$3

To set up a development environment to build FirebaseUI from source, you must
have the following installed:
- Node.js (>= 6.0.0)
- npm (should be included with Node.js)
- Java SE Runtime Environment 8

In order to run the demo and tests, you must also have:
- Python (2.7)

Download the FirebaseUI source and its dependencies with:

`bash
git clone https://github.com/firebase/firebaseui-web.git
cd firebaseui-web
npm install
`

$3

To build the library, run:
`bash
npm run build
`

This will create output files in the dist/ folder.

To build a localized JavaScript binary, run:
`bash
npm run build build-js-{LANGUAGE_CODE}
`
where {LANGUAGE_CODE} is replaced by the
code of the language you want. For example, the French binary
can be built with npm run build build-js-fr. This will create a binary
firebaseui__fr.js in the dist/ folder.

Build names for language codes with underscores, eg. zh_tw, zh_cn, pt_pt
will be mapped to zh-TW, xh-CN, pt-PT. The underscore will be replaced by
a hyphen symbol and the subsequent characters will be capitalized.

`bash
npm run build build-js-zh-TW
`

This will create a binary firebaseui__zh_tw.js in the dist/ folder.

To build a localized npm FirebaseUI module, run:

`bash
npm run build build-npm-{LANGUAGE_CODE}
`

Make sure all underscore symbols in the LANGUAGE_CODE are replaced with
dashes.
This will generate dist/npm__{LANGUAGE_CODE}.js.
You can then import/require it:
`javascript
import firebaseui from './npm__{LANGUAGE_CODE}';
`

Build names for language codes with underscores, eg. zh_tw, zh_cn, pt_pt
will be mapped to zh-TW, xh-CN, pt-PT. The underscore will be replaced by
a hyphen symbol and the subsequent characters will be capitalized.

`bash
npm run build build-npm-zh-TW
`

This will create a binary npm__zh_tw.js in the dist/ folder.

To build a localized ES module of FirebaseUI, run:

`bash
npm run build build-esm-{LANGUAGE_CODE}
`

Make sure all underscore symbols in the LANGUAGE_CODE are replaced with
dashes.
This will generate dist/esm__{LANGUAGE_CODE}.js.
You can then import/require it: