Drilling down

"It's breaking down the silos of information that have been built up," said Marissa Mayer, Google's vice president of search and user experience.

"It's a broad, long-term vision that will unfold over the next few years," she said.

Initially the changes only affect searches done on Google.com in English.

The change means when users carry out a search, it will also be run in the background on all the other categories of information that Google indexes.

A series of tabs will appear between the search box and the results that let users navigate to other categories.

Clicking on a tab will let people drill down into a specific category of results such as patents or products.

Results returned in other categories, such as blogs or video, will not just be from companies that Google owns.

As well as the changes to searches, the firm is introducing drop-down lists that let users quickly switch to other Google properties, such as GMail, and search for results there.

By making the move Google is following other search sites such as Amazon's A9 and Ask which let users navigate quickly to other categories of information or relevant results.