Google has updated the stable version of Chrome to version 27. On top of the usual bug and security flaw fixes, the new version is claimed to load webpages about 5 percent faster on average.

Finding a 5 percent improvement in a browser that's already fast is no mean feat. The better performance comes from making Chrome smarter about the way it uses the network: being more aggressive to download things in some instances and being less aggressive in others.

HTML pages generally include references to many other files that the browser needs to download before it can show a complete page to the user: CSS, JavaScript, and images. These can themselves have dependencies; HTML files can embed other HTML files, CSS files can reference images or other CSS files, and scripts can cause other scripts to be loaded, for example.

Although Google is switching to its own Blink rendering engine, Chrome 27 still uses the WebKit engine. WebKit detects the resources that are needed and puts them in a download queue. A component called the scheduler then sets about downloading all the resources. When doing this, it has to make various trade-offs. Some resources (like HTML itself) are needed more urgently than others (like images). Network bandwidth is finite, and browsers in general should not make too many connections to any one server.

In WebKit, this scheduler is part of the rendering engine itself and as such, each tab (which has its own renderer) has its own scheduler. Chrome 27 moves the scheduler to be shared across the entire browser. This gives the scheduler a better view of the current network activity. Downloads belonging to background tabs, for example, can now be run at a lower priority than those of visible tabs.

Chrome 27 also changes how the scheduler works. If it detects that the network is idle (something it can now do, thanks to its holistic view of the browser's network activity), it will try to pre-load resources that are probably going to be used.

It also scales back some activity: the WebKit scheduler would try to fetch an unlimited number of images at a time. The new one limits this to ten concurrent images, which reduces bandwidth contention. This in turn means that the first few images download faster, and as these images tend to be the ones that are currently visible, it allows the page to render sooner.

The new version also includes a bunch of more or less unspecified "improvements" to the built-in spell checking and predictions in the Omnibox. For developers, there's an extension to the HTML5 FileSystem API that enables files to be stored to, and synced with, Google Drive.

Chrome 27 users will also see a new feature if they use Google as their search engine. The search box has picked up a microphone icon. Click it, and you can speak to the search engine and dictate your searches. It should even support Siri-esque conversational requests.

That said, at the time of writing, this feature seemed extremely unreliable, most times telling us that we had no Internet connection and refusing to let us speak to the search engine.