Migrate to FedCM

This guide helps you understand the changes to your web application introduced by the Federated Credentials Management API (FedCM).

When FedCM is enabled the browser displays user prompts and no third-party cookies are used.

Overview

Privacy Sandbox for the Web and Chrome's removal of third-party cookies from the web introduce significant changes to Google Identity Services and user sign in.

FedCM enables more private sign-in flows without requiring the use of third-party cookies. The browser controls user settings, displays user prompts, and only contacts an Identity Provider such as Google after explicit user consent is given.

For most websites, migration occurs seamlessly through backward compatible updates to the Google Identity Services JavaScript library.

Before you begin

Check that your browser and browser version supports the FedCM API, updating to a newer version if necessary.

Before testing sign-in flows with third-party cookies blocked, open chrome://flags and enable the experimental FedCmWithoutThirdPartyCookies feature. This step is only necessary until it becomes the default. Also, the Third-party sign-in setting has to be enabled in Chrome.

Migrate your web app

Follow these steps to enable FedCM, evaluate potential migration impact, and if needed to make changes to your existing web application:

1. Add a boolean flag to enable FedCM when initializing using:

   • HTML, set the data-use_fedcm_for_prompt attribute to true.

   • JavaScript, set use_fedcm_for_prompt to true in the IdConfiguration object.

2. Remove any use of the opt_out_or_no_session value returned in the PromptMomentNotication object.

   To improve user privacy, the google.accounts.id.prompt callback no longer returns results related to user settings or session status.

3. Update user flows and website code to handle delayed notification of isDisplayMoment() events.

   To improve user privacy, display moment notifications are intentionally delayed a random amount of time when FedCM is enabled. Notifications can be received up to 1 minute after the actual event takes place. When using isDisplayMoment to conditionally display prompts or trigger user interaction carefully consider the variable length of time in your UX design.

4. Remove position style attributes from data-prompt_parent_id and intermediate_iframes.

   The browser controls the size and position of user prompts, custom positions for One Tap on Desktop are not supported.

5. Update page layout if needed.

   The browser controls the size and position of user prompts. Depending upon the layout of individual pages, some content might be overlaid.

   Change page layout to improve the user experience when important information is obscured.

6. Add allow="identity-credentials-get" attribute to parent frame if your web app calls One Tap API from cross-origin iframes.

   An iframe is considered as cross-origin if its origin is not exactly the same as the parent origin. For Example:

   • Different domains: https://example1.com and https://example2.com
   • Different top-level domains: https://example.uk and https://example.jp
   • Subdomains: https://example.com and https://login.example.com

   To improve user privacy, when One Tap API is called from cross-origin iframes, you must add allow="identity-credentials-get" attribute in every parent frame iframe tag:

   <iframe src="https://your.cross-origin/onetap.page" allow="identity-credentials-get"></iframe>
   

   If your app utilizes an iframe that contains another iframe, you must ensure that the attribute is added to every iframe, including all sub-iframes.

   For example, consider the following scenario:

   • The top document (https://www.example.uk) contains an iframe named "Iframe A", which embeds a page (https://logins.example.com).

   • This embedded page (https://logins.example.com) also contains an iframe named "Iframe B," which further embeds a page (https://onetap.example2.com) that hosts One Tap.

   To ensure that One Tap can be displayed properly, the attribute must be added to both Iframe A and Iframe B tags.

7. Add these directives to your Content Security Policy (CSP).

   This step is optional as not all websites choose to define a CSP.

8. Remove Accelerated Mobile Pages (AMP) support for sign-in.

   User sign-in support for AMP is an optional feature of GIS your web app may have implemented. If this is the case,

   Delete any references to the:

   • amp-onetap-google custom element, and

   • <script async custom-element="amp-onetap-google" src="https://cdn.ampproject.org/v0/amp-onetap-google-0.1.js"></script>

   Consider redirecting sign-in requests from AMP to your website's HTML sign-in flow. Note that the related Intermediate Iframe Support API is unaffected.