Google is splitting its search index to target 'stripped down' mobile websites

Justin Sullivan/Getty Images

Google CEO Sundar Pichai.

Google is dividing its index - the almost infinite database of websites it stores for search - into separate mobile and desktop versions. Exactly what that means for search, has so far not been very clear.

The change will happen within months, Google's webmaster trend analyst Gary Illyes told Search Engine Land.

Complimentary Tech Event

Transform talent with learning that works

Capability development is critical for businesses who want to push the envelope of innovation.Discover how business leaders are strategizing around building talent capabilities and empowering employee transformation.Know More

Google regularly makes changes to its index, but this is a particularly big one. The mobile index will be the "primary" index and will be kept more up-to-date than the desktop index. This means that - for the same search - the results you see on a smartphone will be different to what you see on a desktop.

Jennifer Slegg, founder of search expert site The SEM Post and Lisa Barone, CMO of web design agency Overit - attended the Pubcon conference where Google announced the change in the keynote address. They explained to Business Insider exactly how they expect the change to impact search results.

Google wants users to stop experiencing an inferior search experience on a smartphone. By prioritising a mobile index, the search giant is effectively asking site owners to stop putting smartphones second by simplifying their mobile site.

Right now Google only lists desktop sites in its index

Up until now, and before the change is implemented, Google only lists desktop websites in its index. As explained by Overit's Janae Quackenbus, who also attended the conference, "Google has historically 'crawled' the desktop version of a site". Crawling is a term used to describe the process of Google visiting websites to then file them away in its index.

So when you search on a smartphone, Google returns your result as if you are on a desktop, even though what it shows you - and what you click on - is a list of mobile sites.

That wouldn't be a problem if the content on a mobile site was exactly the same as the content on the desktop site. But in a lot of cases, it's not.

In the effort to make their websites load quicker on a mobile (which Google said does not work), a lot of site owners "strip down" the amount of content on their mobile site. Strip down means to remove words and pages, simplifying the site - usually with the format "m.example.com" - IMDb is an example.

IMDB

IMDb's desktop website (left), and mobile version (right).

Google doesn't want site owners to strip down their sites for mobile, and that's the crux of why the change is happening.

Google is targeting 'stripped down' mobile websites

After Google splits its index, when you search on a smartphone, the search engine won't refer to the "full" desktop site when determining what results to give you. Instead, it will refer to the stripped down mobile site in a separate mobile index. With less content, the stripped down mobile site will show up in fewer search results.

Not all websites have stripped down their mobile sites, and therefore won't be affected. If a website has a responsive design - where the content is the same but it loads to fit the screen size of each device - the index split should not have any impact at all.

The move makes sense when you consider that mobile is the dominant choice over desktop for search. And it's not just search - 61% of online retail sales came from mobile devices in the UK in the first half of 2016, according to Criteo's State of Mobile Commerce Report.

As Barone said to Business Insider, "Google's shift to prioritize mobile over desktop follows user behavior to do the very same. Mobile devices are no longer secondary devices; they are the primary device".

RBC analyst Mark Mahaney told Business Insider, "I think the broad point is that we are multiple years now into the 'Mobile Revolution'. Consumers are increasingly comfortable using their Smartphones to access/use Internet services and apps as they used to do with their desktops ... marketers are catching up with consumers and Google is making it easier for them to do that with initiatives like splitting its Search index".