Here's what you need to know about Google's new indexing policy so that you can adjust your SEO strategies accordingly.
The Mobile-First Index: A New Way of Crawling
Google "crawls" your site and indexes the pages it finds. In doing so, the Googlebot basically mimics a web user who follows links.
Once upon a time, Google crawled your site as a desktop user. More appropriately: it used what's called a desktop user agent to traverse your website.
Now, Google will crawl your site as a mobile user.
How does that affect your rank? In a couple of ways.
First, keep in mind that your site might have fewer links on a mobile platform than a desktop platform. That's because responsive technology might eliminate certain parts of your site (for example, the sidebar) on a smaller screen.
Also, you may be using a mobile subdomain or vary HTTP header.
The bad news about that, of course, is that Google won't be able to follow links that don't exist when it crawls around your site as a mobile user.
This makes sitemaps very important.
Also, Google ranks sites, in part, based on how mobile-friendly they are. If your site is hostile to a mobile audience, expect to take a dip in the search engine results pages (SERPs).
What all that means is this: now that Google is using a mobile-first index, you should use a mobile-first SEO strategy.
Why the New Mobile-First Index?
Google is moving to a mobile-first index because that's the wave of the future.
Keep in mind that the number of mobile users exceeded the number of desktop users a couple of years ago (of course this depends on the industry and website). So it's in Google's interest to cater to a mobile user community.
Beyond that, Google announced that there are more mobile searches than desktop searches. So not only are more people using mobile devices, but there are more searches for information on mobile devices as well.
Small wonder, then, that Google is opting for a mobile-first index.
What If Your Site Isn't Responsive?
There are three ways to optimize your website for mobile. You can use a subdomain, vary HTTP header or responsive design. However, the way things are looking it is clear the best move is to go responsive.
While all three optimization options are still allowed, there are rumors that Google will discontinue the mobile subdomain option.
It is a best practice to go responsive now if possible.
What About Hidden Content?
It may be the case that you've taken advantage of accordions and tabs to give your mobile users a better experience. Those design elements effectively hide parts of your content until people click on the appropriate navigation links.
You might think that the Googlebot will "miss" the hidden content as it crawls your site with its mobile user agent and, therefore, not index it.
That's not the case at all.
Google's own Gary Illyes is on record as saying that hidden content will have the same weight as non-hidden content.
In other words, Google won't punish you for creating a design that's appropriate for your mobile users.
This is actually a big change. Not too long ago Google was adamant that they would not index content under a "read more" link or dropdown.
Which was just silly...
Based on small studies I have done, Google is still not indexing the content under read more links.
But hopefully they will soon. I mean, Gary said they would.
How Will Mobile-First Indexing Change Rankings?
So now that Google is crawling your site as a mobile user, will your rankings change significantly?
Yes, if you do not have a good mobile site.
If your site doesn't adapt to mobile users, it will not rank well.
When Does Google Start With Mobile-First Indexing?
Google has already started crawling sites as a mobile user. But the process is far from over.
It will be months before the mobile-first index is complete.
As is usually the case, Google is intentionally vague about the date of the final release. That's in part because the company is still testing the code.
The whole rollout process is progressive. As Google gains confidence that the mobile user agent is working properly, the company will use it to index more pages.
How Can You See Your Site As Google Sees It?
If you're wondering how your site might look to the Googlebot's mobile user agent, just head over to the Google Search Console and have a look.
On the left-hand sidebar of the Search Console, click on the item labeled "Crawl." A new context menu will appear.
Click on "Fetch as Google" from the new menu. On the main part of the screen, you'll see a field where you can enter a URL. Below that, you should see a drop-down menu that's probably defaulted to "desktop."
Click that drop-down menu and select "mobile smartphone." Then, click the big red "Fetch and Render" button.
After a few moments, Google will show you what your site looks like to its mobile user agent.
How Many Indexes?
Google will eventually move to just one mobile index. For now, though, there are still two indexes: the mobile index and the desktop index.
Some users who search with Google will see results from the mobile index. Others will see results from the desktop index.
Neither group will have any clue which index they're looking at.
Over time, though, Google will phase out the desktop index and leave only the mobile index in place.