One of the web’s superpowers is its low friction: a new site is always only a single tap away, allowing users to easily navigate through a rich diversity of experiences. The mobile web provides a great discovery experience for users and unparalleled reach for developers.

Unfortunately, once users discover an experience they love, it is hard for them to build a meaningful relationship since websites lack the engaging capabilities developers have come to expect from mobile such as push notifications and home screen icons. As a result, developers have needed to decide between the engagement potential of a native app and the reach potential of a mobile website.

Chrome 42 addresses this dilemma by allowing users to engage more deeply with the mobile web experiences that are important to them, by both opting in to receive push notifications directly from websites and easily adding regularly-visited high-quality sites to their home screen.

Push Notifications
Timely, personalized notifications save users the effort of manually checking for updates throughout the day and have enabled a host of new experiences from real time communication to live updates on breaking news.

This release of Chrome supports the new emerging web standard for push notifications on Android and desktop, enabling users to opt in to allow a specific website to send them push notifications just like an installed native app. Over the coming weeks, mobile web users will be able to opt in to receiving push notifications from early adopters including Beyond the Rack, eBay, Facebook, FanSided, Pinterest, Product Hunt, and VICE News. Roost and Mobify also provide services that make it easy for developers to integrate web-based push notifications into their site with minimal custom implementation work.
Promoting Add to Home Screen
Mobile users often open their phones to pass time while on the bus or waiting in line. Home screen icons help them easily jump back into their favorite experiences with just a single tap. In this release of Chrome for Android, users who frequently visit a modern, mobile-optimized website such as Flipboard or Medium will be offered the option to easily add the site directly to their home screen in one tap, allowing them to keep in touch and engaged throughout the day.
Developers can now take advantage of these and other recent changes including improved performance, full offline support, and access to device capabilities such as the camera and geolocation to deliver more meaningful experiences on the web than ever before. These new features will continue to improve and evolve over time, diminishing the difficult choice for developers between the reach of the mobile web and the engagement of native apps.

Posted by Miguel Garcia, Push Maestro and Owen Campbell-Moore, Engagement Optimizer

Last year we announced QUIC, a UDP-based transport protocol for the modern Internet.  Over the last quarter, we’ve been increasing the amount of traffic to Google services that is served over QUIC and analyzing QUIC performance at scale. Results so far are positive, with the data showing that QUIC provides a real performance improvement over TCP thanks to QUIC's lower-latency connection establishment, improved congestion control, and better loss recovery.

For latency-sensitive services like web search, the largest gains come from zero-round-trip connection establishment. The standard way to do secure web browsing involves communicating over TCP + TLS, which requires 2 to 3 round trips with a server to establish a secure connection before the browser can request the actual web page. QUIC is designed so that if a client has talked to a given server before, it can can start sending data without any round trips, which makes web pages load faster. The data shows that 75% percent of connections can take advantage of QUIC’s zero-round-trip feature. Even on a well-optimized site like Google Search, where connections are often pre-established, we still see a 3% improvement in mean page load time with QUIC.

Another substantial gain for QUIC is improved congestion control and loss recovery. Packet sequence numbers are never reused when retransmitting a packet. This avoids ambiguity about which packets have been received and avoids dreaded retransmission timeouts. As a result, QUIC outshines TCP under poor network conditions, shaving a full second off the Google Search page load time for the slowest 1% of connections.   These benefits are even more apparent for video services like YouTube. Users report 30% fewer rebuffers when watching videos over QUIC. This means less time spent staring at the spinner and more time watching videos.

Where do we go from here? Today, roughly half of all requests from Chrome to Google servers are served over QUIC and we’re continuing to ramp up QUIC traffic, eventually making it the default transport from Google clients — both Chrome and mobile apps — to Google servers. We plan to formally propose QUIC to the IETF as an Internet standard but we have some housekeeping to do first, like changing the wire format and updating our reference implementation from SPDY-over-QUIC to HTTP2-over-QUIC. In the coming months, we also plan to work on lowering handshake overhead to allow better server-side scalability, improving forward error correction and congestion control, and adding support for multipath connections.   

If you want to follow along or play around, feel free to check out the code and experiment with it, or join as we continue to improve the Internet, one packet at a time.

Posted by SYN, SYN-ACK and ACK (also known as Alyssa Wilk, Ryan Hamilton and Ian Swett)

The newest Chrome Beta channel release includes Web MIDI support, new features to improve security and compatibility and a number of small changes to enable developers to build more powerful web applications. Unless otherwise noted, changes described below apply to Chrome for Android, Windows, Mac, Linux and Chrome OS.

Connecting to MIDI devices from the web

MIDI is a well-established communication protocol used by music devices such as synthesizers, DJ decks, and drum machines. In Chrome 43, users are able to use MIDI hardware to create music without installing any specialized software, as the Web MIDI API allows websites to communicate with connected MIDI devices such as a USB-MIDI drum machine plugged into an Android tablet.

Permissions API
Until now, websites have been unable to determine the permission state of APIs such as Geolocation. Due to this, sites often attempt to use APIs immediately after page load without pre-existing permission, causing users to see confusing permission prompts with no context or explanation.

The new Permissions API allows developers to query and observe changes to their permission status for Geolocation, Push, Notifications and Web MIDI so they can ask for permission in context, improving the user experience.

Moving DOM attributes to the prototype chain

In Chrome 43, attributes defined on DOM objects have been moved to the prototype chain, as specified by Web IDL. This change allows developers to efficiently override or create methods on DOM Objects and improves compatibility with Firefox and Internet Explorer. As this subtle change may cause breakages in existing content, developers should use Chrome 43 to test their website to ensure their users don’t experience issues when this release rolls out to all users.

Upgrading legacy sites to HTTPS

Transitioning large collections of unmodifiable legacy web content to encrypted, authenticated HTTPS connections can be challenging as the content frequently includes links to insecure resources, triggering mixed content warnings. This release includes a new CSP directive, upgrade-insecure-resources, that causes Chrome to upgrade insecure resource requests to HTTPS before fetching them. This change allows developers to serve their hard-to-update legacy content via HTTPS more easily, improving security for their users.

Other updates in this release

  • Chrome OS now fires devicemotion events on pages at a regular interval, allowing developers to track the device’s acceleration in the same way they do on Chrome for Android, Windows, Mac, and Linux.
  • The Web Audio API now allows developers to selectively disconnect specific connections to an AudioNode or AudioParam, avoiding the audio artifacts caused by disconnecting all inputs and then manually re-connecting those that should have been retained.
  • Developers using the Web Audio API can now also explicitly close an AudioContext, releasing all allocated system audio resources instead of depending on unpredictable garbage collection.
  • The nonstandard WebSocket.URL and EventSource.URL were removed in favor of their standard counterparts WebSocket.url and EventSource.url.

As always, visit for a complete overview of Chrome’s developer features, and circle +Google Chrome Developers for more frequent updates.

Posted by Takashi Toyoshima, Software Engineer and MIDI Music Maker

Posted by Marja Hölttä and Daniel Vogelheim, Resident Loader Coders

Speed has always been one of Chrome's primary missions, ever since it was included as one of the founding principles in 2008. But speed is about more than just traditional Javascript benchmarks. Ideally every part of a user's interaction with a browser is fast, starting with loading web pages. Chrome is introducing two techniques called script streaming and code caching designed to reduce that painful waiting time spent staring at a white screen, especially on mobile devices.

Script streaming optimizes the parsing of JavaScript files. Previous versions of Chrome would download a script in full before beginning to parse it, which is a straightforward approach but doesn't fully utilize the CPU while waiting for the download to complete. Starting in version 41, Chrome parses async and deferred scripts on a separate thread as soon as the download has begun. This means that parsing can complete just milliseconds after the download has finished, and results in pages loading as much as 10% faster. It's particularly effective on large scripts and slow network connections.
Code caching is another new technique that helps speed up page loading, specifically on repeated visits to the same page. Normally, the V8 engine compiles the page’s JavaScript on every visit, turning it into instructions that a processor understands. This compiled code is then discarded once a user navigates away from the page as compiled code is highly dependent on the state and context of the machine at compilation time. Chrome 42 introduces an advanced technique of storing a local copy of the compiled code, so that when the user returns to the page the downloading, parsing, and compiling steps can all be skipped. Across all page loads, this allows Chrome to avoid about 40% of compile time and saves precious battery on mobile devices.

These are two examples of ways Chrome is improving page load time, but page load time is just one way to think about the performance of the browser. Stay tuned for more ways the Chromium project is pushing forward all aspects of performance on the web.


The newest Chrome Beta channel release includes support for ES6 Classes and several new features that allow developers to create more immersive web applications. Unless otherwise noted, changes described below apply to Chrome for Android, Windows, Mac, Linux and Chrome OS.

Push Notifications

This release includes two new APIs that together allow sites to push native notifications to their users even after the page is closed—provided the user has granted explicit permission. After the user has granted permission, a developer can use the new Push API to remotely wake up their service worker using Google Cloud Messaging. Once awake, the service worker may run JavaScript for a short period but in this release it is required at minimum to show a user-visible notification. Each notification includes a ‘Site Settings’ button, allowing users to easily disable notifications for a site.

Screen Shot 2015-03-04 at 2.35.05 PM copy.png

Promoting Add to Home Screen

Chrome 32 introduced the ability for Android users to add home screen shortcuts to their favorite websites via a menu item. In this release, users who frequently visit a high-quality web app will see a banner that allows them to add the site to their home screen in one tap.

Sites that wish to take advantage of this new feature must meet eligibility criteria that ensure that users have a good experience when launching sites from the home screen, even when offline. The criteria will evolve over time based on feedback from users and developers, but today they require sites to provide a Web App Manifest, serve all content using HTTPS, and at least partially work offline using a service worker.

ES6 Classes

Developers often find it hard to adapt to JavaScript’s prototype-based inheritance and although many libraries have introduced their own patterns for emulating classes, the language hasn't yet provided a single, uniform way of describing them.

ES6 classes solve this by providing JavaScript a clean, standardized syntax for classes. This new syntax is available in Chrome 42 for JavaScript written in strict mode.
'use strict';

class Polygon {
   constructor(height, width) { = 'Polygon';
       this.height = height;
       this.width = width;

   sayName() {
       log('Hi, I am a ', + '.');

let p = new Polygon(300, 400);

Other updates in this release

  • DevTools now allows developers to visually edit cubic beziers directly from the styles pane, making it easier to understand and modify animations.
  • The Fetch API is now available in the window context, shared workers, and dedicated workers, providing a new promise-based standard for AJAX requests.
  • The startRendering method of an OfflineAudioContext instance now returns a promise that resolves when the audio has finished rendering, making it easier to design web apps that work with the Web Audio API.
  • AudioBufferSourceNode.buffer can no longer be set more than once, protecting developers from the lack of control over when the new source starts.
  • Chrome OS now supports screen.orientation and fires the DeviceOrientationEvent when the device’s orientation changes significantly, allowing orientation-aware websites to operate correctly on Chrome OS devices.
  • This release includes an updated and unprefixed implementation of Encrypted Media Extensions, which allows media sites to discover and interact with digital rights management systems..
  • A new content setting allows users to automatically pause non-primary plugin content to save power. Developers can turn it on to test how it interacts with their content.

As always, visit for a complete overview of Chrome’s developer features, and circle +Google Chrome Developers for more frequent updates.


It seems like yesterday that Chrome was first introduced on mobile devices to users running Android 4.0 Ice Cream Sandwich (ICS). Since then, twenty-four new Chrome releases and three new Android versions (Jellybean, Kitkat and Lollipop) have shipped. We’ve worked hard to make sure each version was faster, simpler and more secure than the last.

In the last year, we’ve seen the number of Chrome users running ICS drop by thirty percent. Developing new features on older phones has become increasingly challenging, and supporting ICS takes time away from building new experiences on the devices owned by the vast majority of our users. So, with Chrome’s 42nd release, we’ll stop updating Chrome on ICS devices. After Chrome 42, users on ICS devices can continue to use Chrome but won’t get further updates.

We’re excited to sharpen our focus on moving the web forward. If you’re interested in learning more about this change, please see the FAQ's.


Tim Willis, Hacker Philanthropist, Chrome Security Team
Around this time each year we announce the rules, details and maximum cash amounts we’re putting up for our Pwnium competition. For the last few years we put a huge pile of cash on the table (last year it was e million) and gave researchers one day during CanSecWest to present their exploits. We’ve received some great entries over the years, but it’s time for something bigger.

Starting today, Pwnium will change its scope significantly, from a single-day competition held once a year at a security conference to a year round, worldwide opportunity for security researchers.

For those who are interested in what this means for the Pwnium rewards pool, we crunched the numbers and the results are in: it now goes all the way up to $∞ million*.

We’re making this change for a few reasons:

  • Removing barriers to entry: At Pwnium competitions, a security researcher would need to have a bug chain in March, pre-register, have a physical presence at the competition location and hopefully get a good timeslot. Under the new scheme, security researchers can submit their bugs year-round through the Chrome Vulnerability Reward Program (VRP) whenever they find them.
  • Removing the incentive for bug hoarding: If a security researcher was to discover a Pwnium-quality bug chain today, it’s highly likely that they would wait until the contest to report it to get a cash reward. This is a bad scenario for all parties. It’s bad for us because the bug doesn’t get fixed immediately and our users are left at risk. It’s bad for them as they run the real risk of a bug collision. By allowing security researchers to submit bugs all year-round, collisions are significantly less likely and security researchers aren’t duplicating their efforts on the same bugs.
  • Our researchers want this: On top of all of these reasons, we asked our handful of participants if they wanted an option to report all year. They did, so we’re delivering.

Logistically, we’ll be adding Pwnium-style bug chains on Chrome OS to the Chrome VRP. This will increase our top reward to $50,000, which will be on offer all year-round. Check out our FAQ for more information.

Happy hunting!

* Our lawyercats wouldn’t let me say “never-ending” or “infinity million” without adding that “this is an experimental and discretionary rewards program and Google may cancel or modify the program at any time.” Check out the reward eligibility requirements on the Chrome VRP page.