 Chrome 51 makes it easy to know when an element enters or exits the viewport with intersection observers. You can make the sign-in process way easier with the new Credential Management API, and you can reduce jank with passive event listeners. I'm Pete LaPage. Let's dive in and see what's new for developers in Chrome 51. Intersection observers let you know when an observed element enters or exits the browser's viewport. No more jank-inducing calls to get bounding client-rect or listening for scroll events. To use, simply create a new intersection observer, provide a callback, and an options object. Then tell the observer which elements to watch. Boom! When the element enters or exits the viewport, the callback is fired. Check the description below for a link to a demo, browser support, and more. Creating, remembering, and typing passwords is a pain in the neck, especially on mobile. Chrome 51 supports the Credential Management API, a new W3C spec that allows your site to interact with the browser's Credential Manager and federated account services like Google and Facebook, improving the log-in experience. The API has three key methods, navigator.credentials.get to get the user's credentials and initiate a sign-in flow, store to save the user's credentials in the Credential Manager, and require user mediation to disable automatic sign-in. There's more info about the Credential Management API, including a demo and links to the docs below. Did you know that simply adding an empty touch event handler to a page can make scrolling janky? Less than 20% of touch events call prevent default, cancelling the scroll, but because the browser doesn't know if it'll be called or not, it has to wait for the JavaScript to finish. Chrome 51 adds support for passive event listeners, allowing you to declare that an event listener won't prevent a scroll, making it easier to eliminate jank. These are just a few of the changes in Chrome 51 for developers. Check the description for more details, and be sure to like and subscribe so that as soon as Chrome 52 is released, you'll know what's new in Chrome.