Google Chrome now includes the ability to completely block resources from loading inside the browser, and the latest incarnation of the AdBlock extension for Chrome is using this "beforeload" event to not only hide ads from the user but prevent them from downloading entirely.

This brings the Chrome AdBlock extension in line with its namesake, the popular AdBlock Plus add-on for Firefox.

The Chrome extension — available here — is maintained by independent developer Michael Gundlach, and although the two share a name, it's not related to the popular AdBlock Plus Firefox add-on from coder Wladimir Palant. But as of last month, they also share the ability to block an ad before it downloads.

Google opened up Chrome to extensions in December, but until recently, the AdBlock extension could merely hide ads — not block them. "Firefox has always had support for blocking resources from downloading," Gundlach tells The Reg. "But when Chrome extensions came out, they lacked that ability, so they weren't as powerful as Firefox was. We've been having to hide the ads after downloading them or add CSS rules that say 'don't show these ads' even though they're downloading."

It's unclear when the "beforeload" event was added to Chrome — in part because it wasn't added by Google. Apple added it to the open source WebKit engine used by Chrome, and at some point, it made its way into the Google browser. It's now available in the latest stable version of Chrome, version 5. "Thank Apple," says Googler Aaron Boodman, the man who created the Firefox Greasemonkey extension, in an online discussion recently dug up by a Slashdot reader. "They added it to WebKit. We just inherited it."

In February, Boodman opened an issue at the open source Chromium project saying that ad blocking, flash blocking, and privacy extensions need to "declaratively block external resources like images, plugins, and iframes." Then, on June 15, he announced that beforeload was available. Chrome 5 — which includes beforeload — had been released three weeks earlier.

Boodman also called beforeload a "partial solution" to the resource-blocking problem. "The 'beforeload' feature is considered a good workaround but not a complete solution," he says. Apparently, Google is looking into additional tools.

Meanwhile, Gundlach has also ported his Chrome AdBlock extension to Apple Safari, which also uses the WebKit engine. You can find the Safari version here. The two extensions are free, but if you feel like donating to the developer, you can do so here.

Firefox was able to capture 25 per cent of the browser market in large part because it offered extensions, and many have pinned a large chunk of its success on AdBlock Plus in particular. With Chrome now offering the ability to block ads entirely, Firefoxers may have more reason to switch.

"I hope one day [the ability to block resources] will be added into Chrome," one poster said before he realized that it had been added. "When this becomes true, I can use Chrome as my only browser. But now sadly, in the area of blocking Ads, Chrome is less powerful than Firefox. I'm looking forward this can be changed!" According to online research outfit Net Applications, Firefox controls 23.81 per cent the browser market, while Chrome is at 7.84 per cent and climbing.

Yes, Google is an advertising company. But you can bet that its internal data suggests that even if an ad blocker is available for its browser, most netizens won't bother to install it. ®