Browsers provide detailed performance information about every resource a webpage loads. Most of this information is hidden during cross-origin requests however. This is a common problem since pages often load content from a variety of origins. Pages can access cross-origin timing information if an additional header is added to cross-origin responses.

Starting software products is hard, and it’s easy to make mistakes. We’ve started a lot of products – and we’ve made a whole lot of mistakes along the way. But that’s not going to stop us. We’re stubborn like that. Today we are launching Request Metrics for the third time, and I’m reflecting on what we did wrong in the first two attempts, and how we’re going to be better, faster, and strong next time.