Intent to implement and ship: WebAuthn WebDriver backup flags settings

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Nina Satragno

Feb 14, 2024, 1:21:57 PMFeb 14
to blink-dev,

Contact emails,

Specification, look for backupState and backupEligibility

Or, if you prefer, see the merged PR.


A set of new attributes for WebAuthn WebDriver Virtual Authenticators and their Credential Parameters that allow setting default and current values for the backup state and backup eligibility credential flags, and a new Set Credential Properties command that lets developers manipulate these values for existing (virtual) credentials. The motivation is to allow developers to write integration tests that exercise a web application reacting to backup state changes as real credentials would during their lifetime.

The feature is already implemented at the devtools level, we are requesting permission to implement and ship its WebDriver layer.

Blink component


TAG review



Interoperability and Compatibility

Firefox and Safari support the WebAuthn WebDriver API. However, Chrome is the first to implement backup flags settings.

Gecko: No signals.

WebKit: pascoej@ (Apple) reviewed & approved the PR.

Web developers: MasterKale@ (Duo / Cisco) showed support & approved the PR.

Other signals: emlun@ (Yubico) also approved the PR.

WebView application risks

Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?

The virtual authenticator is not supported on webviews.




Developers will be able to connect to the browser through the WebDriver API as specified, or use Selenium bindings.


This is only exposed through WebDriver.


This is a debugging feature.

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?

No. The WebAuthn WebDriver API is only available on desktop.

Is this feature fully tested by web-platform-tests?

No. This is not a web feature.

DevTrial instructions

The WebDriver layer is not implemented yet. Developers wishing to try the underlying API can access it directly through Chrome's DevTools Protocol.

Flag name on chrome://flags


Finch feature name


Non-finch justification

WebDriver feature.

Requires code in //chrome?


Tracking bug

Launch bug

Estimated milestones


Nina Satragno

Rick Byers

Feb 20, 2024, 2:51:01 PMFeb 20
to Nina Satragno, blink-dev,, Mathias Bynens
Looks pretty straightforward to me and has some good support from other engines. LGTM1

/cc @Mathias Bynens in case he has any thoughts from a WebDriver perspective 

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Yoav Weiss (@Shopify)

Feb 20, 2024, 4:03:15 PMFeb 20
to Rick Byers, Nina Satragno, blink-dev,, Mathias Bynens

Chris Harrelson

Feb 23, 2024, 5:17:17 PMFeb 23
to Yoav Weiss (@Shopify), Rick Byers, Nina Satragno, blink-dev,, Mathias Bynens
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