Unless otherwise noted, changes described below apply to the newest Chrome Beta channel release for Android, Chrome OS, Linux, Mac, and Windows.

CSS custom properties
Modern websites often have CSS files with repeated values, such as a few colors reused throughout the page in a color scheme. Altering this data can be tedious and error-prone, since it’s scattered throughout one or more CSS files. To improve this, Chrome now supports CSS custom properties, allowing developers to define property variables in CSS without using external frameworks. Developers can then use the var() function to reference these custom properties anywhere in the document.

Changing a custom property can update multiple components in a website

CSS custom properties also inherit across shadow roots, so a web component can provide a “style API” that makes it possible to tweak and theme the component without knowing about its internals. The Polymer library uses this platform feature to simplify customizing components.

Background sync with service workers
Previously, sites could lose local changes or become out of sync if a user didn’t stay on the site until updates could be sent over the network. For example, an email client might lose a pending message if the user hit "send" and quickly navigated away. The new Background Sync API improves networking reliability by allowing service workers to schedule a one-off sync of a user’s local changes when the device next connects to the network, even if the site isn’t open.

Improved ECMAScript 2015 support
The ES2015 specification (ES6) is a major update to JavaScript that allows developers to write application logic that is more legible, powerful, and memory efficient. The latest version of Chrome’s V8 engine has 91% JavaScript ES2015 feature support. Developers can now use destructuring and default parameters to avoid boilerplate code when extracting data from arrays and objects or when setting function parameter defaults. Proxy objects and the Reflect API can customize previously hidden object behavior such as property lookup and assignment. The latest version of Chrome also makes block-level constructs such as class and let available outside of strict mode.

Keygen and application/x-x509-user-cert
The <keygen> element is used to generate a key-pair as part of an HTML form. While this can be used to enhance user security, <keygen> and user certificates sent with the MIME type of application/x-x509-user-cert can be exploited to disrupt a user’s secure communication, interfere with the functioning of their devices, or track the user without consent. Going forward, <keygen> will return an empty string by default and user certificates sent with the MIME type of application/x-x509-user-cert will no longer be automatically downloaded and installed.

Other features in this release

Minor changes

Posted by Josh Karlin, Syncing Samurai