The Web Performance Working Group has published User Timing Level 2 as a W3C Recommendation. This specification defines an interface to help web developers measure the performance of their applications by giving them access to high precision timestamps. User Timing Level 2 is intended to supersede the first version of User Timing specification.

9 July 2018 The  Web Performance Working Group  invites implementations of  User Timing Level 2  Candidate Recommendation. This specification defines an interface to help web developers measure the performance of their applications by giving them access to high precision timestamps.

26 July 2012 The Web Performance Working Group invites implementation of three Candidate Recommendations: Page Visibility which defines a means for site developers to programmatically determine the current visibility state of the page in order to develop power and CPU efficient web applications. Performance Timeline which defines an unified interface to store and retrieve performance metric data. This specification does not cover individual performance metric interfaces. User Timing which defines an interface to help web developers measure the performance of their applications by giving them access to high precision timestamps. Learn more about the Rich Web Client Activity .