What Executives Need to Know About Google’s Mobile-First Index

In November, Google announced plans to move to what they called “mobile-first” indexing, continuing a trend of increasingly emphasising the mobile user experience.

Depending on exactly what they mean by this, it could have serious impacts on mobile and desktop performance, even on businesses that don’t get large amounts of mobile traffic, and who may have so far deprioritised mobile site friendliness.

You may be affected if you have:

  1. A mobile site with reduced content on each page, different internal linking structure, or fewer pages - whether served on separate URLs or dynamically-served on the same URLs as the desktop site; and / or

  2. No mobile site and a desktop site that is not responsive - and hence is flagged as not mobile friendly by Google

In either of these situations, you are at risk of losing not only mobile search traffic, but desktop search traffic as well and should take emergency measures to address this risk. If you are in charge of a major site, and are in this situation, you can drop me a personal email to get advice for your specific case - firstname.lastname at our domain.

What is a “mobile-first index”?

Of course, Google isn’t telling us exactly what they mean, and we won’t know for sure at least until it launches. Based on what we know about current mobile crawling and desktop ranking factors, and applying some logic, we can figure out a few things:

  1. Given that they already crawl with a smartphone user-agent, it must be more than just crawl changes

  2. The minimal definition of “index” would be to include or exclude URLs from a given set of search results based on the content returned to a mobile-user-agent crawl of that page

  3. A “mobile-first” index should imply that when a mobile and a desktop URL are both discovered, the mobile (“alternate”) URL is treated as canonical regardless of the presence or absence of a rel canonical link back to the desktop version

  4. The next level would be to use the mobile crawl for discovery in place of the desktop crawl (the weaker version of using it in addition to the desktop crawl is uninteresting, and may even already be happening)

  5. The top level would be to use the contents of the mobile index to calculate off-site ranking metrics - particularly metrics based on external links

For anything that stops short of using the mobile crawl data to calculate off-site metrics, there should be little impact on external link metrics for a correctly-configured site, because of the canonical link from desktop to mobile and the assumption that even if they go to level 3, they will use the alternate link for canonicalisation. If the mobile crawl is used to calculate off-site metrics, however, there will be an impact on all sites regardless of their on-site setup because the wider-scale link graph will change.

For misconfigured sites with separate URLs but no alternate / canonical links between them, the lack of a canonical link has relatively low impact. Separate mobile URLs generally get very few links, but if the default flips, then the alternate link from desktop to mobile will be crucial for passing authority in the other direction.

My best guess is that levels 2 or 3 are most likely in the initial roll-out - most likely just level 2.

How will my site be affected?

Based on this assessment of what it probably means, I see three main impacts:

  1. On-page / content issues: It seems likely that on-page factors will be used from the mobile crawl, so if you are serving sparse content (we commonly see worse titles, missing headings, etc.), fewer pages, or a poor user experience on mobile, you could see traffic drops from ranking drops or even pages disappearing from the index entirely

  2. Loss of external links: If they recalculate link metrics based on the mobile link graph, then all sites will be impacted in unforeseeable ways by the mobile-friendliness of major sites and the visibility of their outlinks on mobile. There’s nothing you can do about this one, and nor can we forecast it, so the best you can do is flag potential upcoming volatility to senior management

  3. Different internal link structure: If they recalculate link metrics based on the mobile link graph and your mobile site has a different internal-linking structure, then you could see impacts ranging from ranking drops based on worse distribution of internal authority through to shallower indexation caused by the removal of key crawl paths through the site

What should digital marketers do?

  1. Identify the risks to your specific site - “yes” answers to any of the following:

    1. Do we have different content, less content, or worse targeting when our site is viewed on mobile (regardless of whether it is served dynamically, or on different URLs)?

    2. Do we have a different internal linking structure on mobile versus on desktop?

    3. If we use separate mobile URLs, do we have canonical and alternate links back and forth between all pages?

    4. If we use separate mobile URLs, are there any sections of the site without mobile versions?

    5. Do we present a non-mobile-friendly user experience on any pages on our site (non-responsive and lacking in an alternate mobile version)?

  2. Clearly flag to senior management the information they need to know:

    1. Google is making this change

    2. There is likely to be volatility in organic search traffic for many sites

    3. [Depending on answers to #1] We are specifically at risk in the following ways

  3. Depending on their desire to drill into the details, send them a link to this post for more background and explanations

  4. If they are concerned, give them my details, and tell them to drop me a line to discuss your specific situation

Due to the time sensitivity and potential revenue impact, this is the kind of update that I generally recommend outlining clearly in writing as well as giving an in-person update. For the written version, it will be most impactful if outlined according to our guide to writing better business documents.

We need mobile-first SEO data

It’s been great to see JavaScript rendering come to some tools (shout-out to v7 of Screaming Frog and its rendered screenshots). This is crucial in a mobile-first world.

But our link data is less up-to-date. It’s easy enough to crawl your own site with a mobile user-agent, but I’m not aware of any web-wide link data gathered mobile-first. I’d love to see even a stand-alone study into the scale and scope of the differences between the desktop link graph and the mobile link graph. Ultimately though, the further Google doubles down on mobile-first, and especially if they ever get to “mobile-only” we are going to need regularly-updated link data gathered mobile-first. I’ll be sending this post to the data teams at Moz, Ahrefs, Majestic etc.

Will they go as far as a mobile-only index?

For those who enjoy a bit of speculation about the future (you should check out SearchScape), here’s my best guess at a timeline:

  1. First roll-out of mobile-first index: Google moves to building their primary index using the page content found using the mobile crawl, but continues to use the desktop crawl for link metric calculations, and continues to canonicalise the desktop and mobile pages

  2. Mobile crawl link discovery: will be baked in quietly in the months after initial launch - it’ll be hard to detect from the outside, and makes relatively little difference anyway

  3. Using the mobile crawl for link metrics: unlikely to happen until they see a convergence between the mobile and desktop link graphs - until then, they are just throwing away valuable data - but I imagine they will get there eventually because, in the long-run, a double-crawl seems unnecessary

Of course, it’s possible this whole thing is PR FUD from Google and nothing much changes. What do you think?

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About the author
Will Critchlow

Will Critchlow

Will founded Distilled with Duncan in 2005. Since then, he has consulted with some of the world’s largest organisations and most famous websites, spoken at most major industry events and regularly appeared in local and national press. For the...   read more