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Google Public DNS: Explained simply

Do you trust Google to take over one of the core jobs of your Internet service provider? We explain what Google's Public DNS service is and how it works

Do you trust Google to take on one of the core jobs of your Internet service provider? Having launched its Google Public DNS service, it thinks you should.

To understand why Google Public DNS is such a big deal, you need to understand something about how Web pages work. Web sites are large collections of text documents, images and videos. These are stored on a computer somewhere in the world, and this computer has an address, just like each of your friends has a telephone number.

When you type in a Web site's address, your Web browser asks your ISP where the computer is that stores all of the Web site's files. It needs the computer's address -- something called an IP address. The IP address of CNET UK, for example, is, which is much harder to remember than cnet.co.uk.

It's just like when you use your mobile phone's address book. Instead of remembering a person's phone number, you'd just save that number in your phone under the name of your contact. To call someone, you select their name, but your phone actually dials a phone number. This is exactly what your ISP does when you punch in cnet.co.uk, for example -- it turns it into the exact number needed to find our Web site.

What Google Public DNS does is take that entire job away from your ISP, so, when you type in cnet.co.uk, your ISP doesn't turn that into a numerical address -- Google does. And Google reckons its vast knowledge of the world's IP addresses, which it's gathered from essentially visiting every Web site in existence over the last decade, makes its offering faster and more comprehensive than the database your ISP has.

Google is becoming fixated on how fast Web sites load, and that appears to be the main reason behind it pioneering an alternative to ISP DNS systems. Essentially, the faster a Web address can be resolved into an IP address, the faster your pages will load.

What's unclear at the moment is how Google might make money from this in the future. A competitor, OpenDNS, displays ads alongside the error pages returned if you type in a non-existent Web site address, or if an existing Web site isn't responding to your request. Google, arguably the king of advertising, could easily replicate this model. But will it? Who knows? If you want to experiment, check out the Google Public DNS homepage. But be warned -- it's not for beginners.