Enable seamless credential sharing across websites in Chrome

If you employ multiple domains that share the same account management backend, you can now also declare that they can share credentials across one another to enable users to save credentials once and have the Chrome password manager suggest them to any of the linked websites.

Milica Mihajlija

Chrome's password manager already autofills credentials for websites with saved credentials, as well as in the following two cases:

• When two websites are in the same-site relationship, Chrome will show autofill credentials for the other site if there's at least one credential saved on one site. For example, because www.example.com and m.example.com are the same-site, Chrome can share saved credentials between the two websites and suggest the saved password to another.
• When a developer associates an Android app with a site that uses the same credentials, Chrome can suggest Android credentials on that site. Apps are associated with websites using Digital Asset Links (DALs).

You can now also associate websites in a cross-site relationship to enable users to save their credentials once and have the password manager suggest them to any of the associated websites.

If you employ multiple domains that share the same account management backend (such as https://www.example.com and https://www.example.co.uk), starting in version 91, you can enable Chrome to suggest passwords saved to domains associated with Digital Asset Links.

Note: There's a similar potential web platform feature called First-Party Sets. However, while it allows for embeds from cross-site to be treated as the same party when the top-level domain is owned by the same organization, there's no plan to have any effect on handling passwords. The Digital Asset Links is Google's technology that can be used for passwords, but it has no effect on handling cookies.

To make a DAL association, developers need to put a JSON file that follows the DAL syntax at /.well-known/assetlinks.json on the respective domains.

Prerequisites

• Use Chrome 91 or later.
• Make sure "Offer to save passwords" is turned on in chrome://settings/passwords.
• Make sure your website's sign-in domain is available through HTTPS.

Set up seamless credential sharing across your two websites

1. To declare that the website, for example https://www.example.com,can share credentials with https://www.example.co.uk, create a file named assetlinks.json with the following content:

   [{
     "relation": ["delegate_permission/common.get_login_creds"],
     "target": {
       "namespace": "web",
       "site": "https://www.example.com"
     }
    },
   {
     "relation": ["delegate_permission/common.get_login_creds"],
     "target": {
       "namespace": "web",
       "site": "https://www.example.co.uk"
     }
   }]
   

   The relation field is an array of one or more strings that describe the relationship between the websites. For websites to share sign-in credentials, specify the string delegate_permission/common.get_login_creds. The target field is an object that specifies the asset the declaration applies to. The following fields identify a website:

   namespace	Must be web for websites.
   site	The website's URL, in the format https://domain[:optional_port]; for example, https://www.example.com.

   See the Digital Asset Links reference for details.

2. Host the Digital Asset Links JSON file at the following location on the sign-in domain: https://domain[:optional_port]/.well-known/assetlinks.json.

   In this example, the domain is www.example.com, so the JSON file should be hosted at https://www.example.com/.well-known/assetlinks.json.

   The MIME type for the Digital Asset Links file needs to be JSON. Make sure the server sends a Content-Type: application/json header in the response.

   Key point: The request for a DAL file must return an HTTP 200 OK status code, otherwise it will be treated as an error. This applies to redirects which return status codes in the 300-399 range.

3. To declare the association in both websites, host the assetlinks.jsonat https://www.example.co.uk/.well-known/assetlinks.json as well:

   [{
     "relation": ["delegate_permission/common.get_login_creds"],
     "target": {
       "namespace": "web",
       "site": "https://www.example.com"
     }
    },
   {
     "relation": ["delegate_permission/common.get_login_creds"],
     "target": {
       "namespace": "web",
       "site": "https://www.example.co.uk"
     }
   }]
   

4. Ensure that your host permits Google to retrieve your Digital Asset Links file. If you have a robots.txt file, it must allow the Googlebot agent to retrieve /.well-known/assetlinks.json. Most websites can allow any automated agent to retrieve files in the /.well-known/ path so that other services can access the metadata in those files:

   User-agent: *
   Allow: /.well-known/
   

Note: It may take a while for Googlebot to fetch the resource and recognize the association.

Set up seamless credential sharing across multiple websites

You can Set up seamless credential sharing across multiple websites by specifying each one in the Digital Asset Links file. For example, to associate the example.com, example.co.uk,andexample.co.jp, specify all of those websites in the assetlinks.json JSON file and host it on each website at https://EXAMPLE_DOMAIN_NAME/.well-known/assetlinks.json.

[{
     "relation":[
        "delegate_permission/common.get_login_creds"
     ],
     "target":{
        "site":"https://www.example.com",
        "namespace":"web"
     }
  },
  {
     "relation":[
        "delegate_permission/common.get_login_creds"
     ],
     "target":{
        "site":"https://www.example.co.uk",
        "namespace":"web"
     }
  },
  {
     "relation":[
        "delegate_permission/common.get_login_creds"
     ],
     "target":{
        "site":"https://www.example.co.jp",
        "namespace":"web"
     }
  }]

Note: You can use include statements if you need to issue statements from different websites to the same set of targets. For example, a website may be available on many different per-country top level domains, and you want to share credentials between all of them. Using include statements, you can set up pointers from many different websites to one central location, which defines statements for all of them.

Learn more about credential sharing:

• Seamless credential sharing
• Digital Asset Links