Internet search giant Google is to launch a free service which allows companies to see how visitors interact with websites and to measure the effectiveness of their online marketing.

Google Analytics will let website owners see exactly where site visitors are coming from, which links on the site are getting the most traffic, which pages visitors are viewing and how long people stay on the site.

It can be can be used by website builders to discover which keywords attract visitors, which promotions hold on to customers and how to design pages that draw attention. The software has been developed following Google's acquisition of web analysis firm Urchin earlier this year.

The US-headquartered search engine, which earned nearly all its last quarter revenue of $1.58 billion (€1.34bn; £904m) from ad sales, is betting its giveaway can also drive increased use of its search marketing services.

Says Paul Muret, a Google engineering director and one of the founders of Urchin: "Any time we add more measurability and more control, advertisers understand more of what they are doing and they end up spending more."

Comments Eric Peterson, a senior analyst at Jupiter Research: "This has the potential to be a pretty big deal. They made the acquisition earlier this year and are trying to think of good ways to take advantage of it."

Data sourced from Financial Times Online and Reuters Online; additional content by WARC staff