Search engine giant Google is set to update its search algorithms tomorrow to favour mobile-friendly sites, a change the internet has dubbed ‘mobilegeddon’ that is set to punish the rankings of many big brands.

A non-scientific scan of brands’ websites by Marketing has found Coles, Mercedes-Benz, Dominos, Nestle, Mars and the Australian Government among those set to feel the impact because their sites are not mobile-friendly enough.

The changes are due to take place on Tuesday, 21 April, US time, effectively reaching us in Australia tomorrow.

Google announced the update on 26 February in a statement on its Google Webmaster Central blog:

“Starting April 21, we will be expanding our use of mobile-friendliness as a ranking signal. This change will affect mobile searches in all languages worldwide and will have a significant impact in our search results. Consequently, users will find it easier to get relevant, high quality search results that are optimized for their devices.”

Google says it is making the changes to improve users’ ability to reach timely and relevant search results, “as more people use mobile devices to access the internet”.

Smartphone ownership in Australia is more than 80%, according to Deloitte, and browsing the web is the most popular activity on smartphones and tablets.

Estimates vary but some studies are reporting about 60% of all Google searches are now being done from mobile devices.

Despite the two months’ notice from Google prior to making the update, commentators are warning that many websites have failed to adapt their sites to be mobile-friendly in time.

Marketing agency Somo used Google’s Mobile-friendly Test tool to compile a list of brands that will be hit by the update. Most companies that they looked at are from the UK or US but many have Australian presences too.

These are: Versace, Next, American Apparel, Daily Mail, RyanAir, Channel 4, Windows Phone, Nintendo UK, Kelloggs UK, Dyson, P&O Cruises, David Beckham, Clairol UK, Cotton Traders, Danone, and Legal & General.

“Several of these brands do have apps and/or mobile sites, however they still risk dropped rankings as Google does not recognise them as mobile-friendly,” Noreen McCaffrey writes on the Somo blog.

Marketing tested out the Mobile-friendly Test tool on some local websites, and found a few that failed the mobile-friendly test for the following reasons:

• Coles: content wider than screen; links too close together,
• Mercedes-Benz: content wider than screen; links too close together,
• Dominos: content wider than screen; links too close together,
• Nestle: text too small to read; links too close together; mobile viewport not set; content wider than screen,
• Mars: text too small to read; links too close together; mobile viewport not set, and
• Australian Government: content wider than screen; links too close together.

Search Engine Land has reported that Zineb Ait Bahajji, of Google’s Webmaster Trends team, said at SMX Munich last week that this mobile-friendly ranking algorithm will impact search results more than either the Google Panda update (a content quality filter introduced in February 2011) or the Google Penguin update (an anti-spam filter introduced in April 2012).

Itai Sadan, CEO of website building company Duda, told Business Insider he expected small businesses to be hit hardest. “I think the people who are at risk are those who don’t know about it.”