 The CSS Contain property makes rendering performance screen. It's easier to collect real user measurement data with the Performance Observer API. The browser can now progressively render content served from a service worker with streamed HTTP responses, and there's plenty more. I'm Pete LePage on the Highline. Let's dive in and see what's new for developers in Chrome 52. When an element changes and needs to be re-rendered, the browser has to consider how that single change may affect all the other nodes in the DOM. With the CSS Contain property, you can scope the changes to only a portion of the DOM. Contain layout can help reduce the number of elements that may need to be re-rendered to just a handful. Contain paint, clips the element, and prevents an element's children from displaying outside of the bounds. Contain size means that the element's children do not affect the parent size. Contain style means that style changes won't get propagated back up past the containing element. Check out Paul Lewis' intro post linked below for more details. Collecting accurate real user measurement data is critical to detecting performance problems and regressions that might hurt your user experience. Chrome 52 now supports the Performance Observer API, which enables a simple and performant way to collect performance data at runtime. Instead of polling for updates, you can declare what metrics you're interested in, then the browser notifies you when those new data points become available. Service workers can now stream HTTP responses, allowing the page that made the request to start working with the response as soon as the first chunk of data is available. Unlike fetch requests that need to wait until the entire response is received, stream responses can be progressively rendered as it's downloaded. There's also support for VAPID, an open standard to authenticate your server with a web push service. Style sheets can now specify alpha values for colors using hex values instead of the RGBA syntax. And you can now experiment with persistent storage as an origin trial. These are just a few of the changes in Chrome 52 for developers. Check the description for more details. And if you want to stay up to date with Chrome and know what's coming, click the subscribe button right up there. I'm Pete LePage and as soon as Chrome 53 is released, I'll be right here to tell you what's new in Chrome.