More than half of Australia's biggest companies will "disappear" from Google on mobile devices as the US technology giant changes the way it ranks searches.
From Wednesday, Google will prioritise companies that have "mobile-friendly" websites when people use the search engine on their smartphones or tablet computers.
Google says businesses with desktop-only sites will still appear in searches but they will be ranked lower then those tailored for mobile use.
"As more people use mobile devices to access the internet, our algorithms have to adapt to these usage patterns," the company wrote in a blog post. However, digital strategist Ewan Watt, or roi.com.au, said the changes would disadvantage most Australian companies, considering 66 per cent of the nation's websites weren't optimised for mobile devices.
The Council of Small Business Australia is also concerned and has asked Google for more time to make the switch.
However, the Australian Chamber of Commerce and Industry says consumers and business will, ultimately, be better off.
The changes do not only affect small to medium-sized companies.
Roi.com.au analysis shows 51.5 per cent of ASX 200-listed companies, including Domino's Pizza, Coca-Cola Amatil and BHP Billiton, do not have mobile-friendly sites and, consequently, will fall in Google search rankings.
"There is a massive gap at the moment and there are number of major brands . . . Pepsi, Jim's Mowing that . . . are not set up and ready for this" Mr Watt said.
A Domino's spokeswoman said the company was ready for the algorithm change known as "mobilegeddon".
"With almost 60 per cent of our sales attributed from online and 50 per cent of those being from mobile, it's important we constantly stay up to date and relevant with any significant online changes and updates as they happen," the spokeswoman said.
"The mobilegeddon scheduled for this week is no different. We have taken the necessary steps to ensure our customers' online experience on mobile is not disrupted in any way."
Mr Watt said although Domino's had a mobile site, it was redirected from the desktop version during a Google mobile search.
This classified it as not being "mobile ready" for the changes, he said.
"A website design needs to be responsive without redirecting to separately hosted mobile site," he said.
"[The] common mistakes we are seeing [are] content not scaling properly for a mobile device [and] separate versions of the desktop and mobile site in operation with different content."
The Council of Small Business Australia executive director Peter Strong urged Google to allow smaller companies more time to adapt.
"You can have a great website, have a good business and offer a product at a great price, but it's a bit unfair if customers can't find you," Mr Strong said, adding the changes were reflective of Google's dominance.
"When you're a monopoly, you've got to look at the public good. What if I'm looking for a chemist late at night and I'm in a foreign city, you'd want to find the nearest chemist."
However, the Australian Chamber of Commerce's director of economics and industry policy, John Osborn, said businesses needed to embrace mobile technology.
"This is overwhelmingly the way the internet is going and business can't resist that. They need to adapt and being web savvy is not a nice to have but a need to have," Mr Osborn said.
"That's the competitive environment that all businesses must survive in and it will, ultimately, make them stronger and more targeted to consumer preferences."
A Google spokesman said it had been working with website owners to ease the transition.
"As people increasingly search on their mobile devices, we want to make sure they can find content that's not only relevant and timely, but also easy to read and interact with on smaller mobile screens," the spokesman said.
"We've been offering resources for webmasters to test their mobile sites and tools to make their pages mobile-friendly. We'll use a web page's 'mobile-friendliness' as one of many factors to help rank searches done on mobile device."