“Mobilegeddon,” as many are calling it, happened Tuesday, courtesy of Google, the predominant web search engine.

Most users won’t notice any difference if they do a Google search on a desktop or tablet, according to national news media reports.

But mobile users will. That’s because Google has changed its search algorithm on smartphones to favor mobile-friendly websites over the larger, more-complicated desktop-friendly sites, according to The Associated Press.

The AP reported that for websites to stay near the top of Google searches on smartphones, they must be designed to load quickly on mobile devices, be easily accessible by scrolling vertically — not horizontally — and buttons for making purchases or going to other parts of the site must be easily seen and touched on mobile screens.

Business Insider added that Google’s mobile searches also will favor sites that have large text and automatically resize to fit the screens on which they are viewed. Sites that don’t meet the new criteria will be demoted in mobile search results, Business Insider says.

This is most important for businesses that only have websites designed for desktop computers because, according to USA Today, being ranked lower on a Google search can mean a sharp loss in revenue because users will be less likely to find their sites.

Businesses that rely on being found by people searching for them on their smartphones, and that haven’t optimized their sites for mobile devices, could virtually disappear from search results because they will pushed so low in Google’s rankings, Business Insider reported.

Itai Sadan, the CEO of Duda, a website-building company, told Business Insider the nickname “Mobilegeddon” refers to the “apocalyptic” hit millions of websites could take.

Average users will be affected if they rely on Google, rather than bookmarks or their memories of their favorite website URLs, to land on their favorite websites, and those sites don’t measure up to Google’s new mobile search formula.

The AP reported that the number of mobile web searches in the U.S. is rising by 5 percent, while desktop searches are dropping slightly, according to comScore Inc. In the last quarter of 2014, comScore reported that 29.5 percent of all U.S. Internet searches, or 18.5 billion, were made on mobile devices, and that Google processes two-thirds of those searches in the U.S. and more in other countries, according to the AP.

What Google does is important because of its market dominance. USA Today reports that the search engine has a 65 percent market share of U.S. web searches, according to comScore.

To see how a website fares on Google’s new mobile metric, go to https://www.google.com/webmasters/tools/mobile-friendly.