AWS SSO vs Okta

AWS Single Sign-On (SSO) is a cloud SSO service that makes it easy to centrally manage SSO access to multiple AWS accounts and business applications. It enables users to sign in to a user portal with their existing corporate credentials and access all of their assigned accounts and applications from one place.
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2017 - Amazon enters single sign-on market to take on Okta

Amazon released a single sign on product for the AWS cloud. With AWS SSO you can easily manage SSO access and user permissions to all of your accounts in AWS Organizations centrally. That’s very different from what other single sign on products like Okta or OneLogin are doing. These companies provide a much more comprehensive approach to single sign on, giving you a central way to log into all of your cloud services (and in some cases on-prem too). This saves you the pain of having separate user names and passwords for every account. You log in once and you have access to all of the included cloud services.