Salesforce Identity alternatives

Salesforce Identity
One login for all your web, mobile and on-premises apps. That makes it easier for IT. And users. Improve usability and security with standards-based single sign-on to all your enterprise apps. Provide single sign-on, authorization and mobile specific policies for standard Salesforce apps, or custom apps built with Mobile Services. Instant internal and external collaboration with social feeds built into Identity services.
Salesforce Identity alternatives are:
Okta