Google recently announced that it was making some changes to its mobile search algorithm, penalising sites for making a few common errors. With this in mind, Pure Oxygen Labs used its mobile SEO diagnostic tools to examine how Fortune 100 companies will fare once the changes come into effect.

Two-thirds of the companies are at risk of being downgraded in Googles rankings for not serving mobile versions of indexed pages, according to the research. Only 56 per cent serve any mobile-formatted content to smartphone searchers, and just six of the 100 companies fully comply with Googles requirements – Disney, GE, Humana, JP Morgan, HCA Healthcare and, rather unsurprisingly, Google itself.

In terms of their sites, 56 of the companies are mobile-optimised: 45 of these through a dedicated mobile site, and 11 through responsive design. Its interesting to note that all the compliant sites are of the latter variety, perhaps reflecting Googles position on responsive design.