The API provides a programmatic interface to the browser's credential manager. In short, an origin can request a user's credentials to sign them in, or can ask the browser to save credentials on the user's behalf. Both of these requests are user-mediated.
Docs: https://developer.mozilla.org/en-US/docs/Web/API/Credential_Management_API https://developer.mozilla.org/en-US/docs/Web/API/Credential https://developer.mozilla.org/en-US/docs/Web/API/CredentialsContainer https://developer.mozilla.org/en-US/docs/Web/API/FederatedCredential https://developer.mozilla.org/en-US/docs/Web/API/PasswordCredential