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PHOTO: Joshua Newton

In 2016, Google introduced the concept of mobile-first indexing. According to the company, its algorithms would "use the mobile version of a site’s content to rank pages from that site, to understand structured data, and to show snippets from those pages in our results."

In 2018, after a year and a half of testing, Google announced that it started to perform mobile-first crawls for "sites that follow the best practices for mobile-first indexing." To help site owners understand the best practices, Google published a guide on how to prepare for mobile-first indexing.

At SMX West 2019 in San Jose, Calif., Eric Enge, general manager at Stone Temple Consulting, gave a presentation titled “Mobile-First Indexing and Mobile-Friendly SEO.”

The bad news: there’s a lot that can go wrong when your site is crawled mobile-first. The good news: Google (generally) will not migrate your site if it’s not ready, so there’s still time to address mobile-related issues. 

Here are five mobile-first gotchas covered in Enge’s presentation.

Related Article: 3 Search Marketing Takeaways from SMX West 2019

1. Your Mobile Site Is Missing Content

According to Google’s “How to prepare for mobile-first indexing page” (referenced earlier):

“Your mobile site should contain the same content as your desktop site. If your mobile site has less content than your desktop site, you should consider updating your mobile site so that its primary content is equivalent with your desktop site.”

In his presentation, Enge shared an example of a retail website. While its desktop site had 783 pages, its mobile site had just three pages:

  • Mobile homepage
  • Contact Us form
  • About Us page

Fortunately for the site, Google has not yet migrated it to mobile-first indexing. If it did, then 99 percent of this retailer’s site would disappear from Google!

The fix: Make the other 780 pages visible when visiting from a mobile device.

2. Your Mobile Site Misbehaves or Has Bugs

Using the example of the same retail site, Enge found the following issues with the mobile experience:

  • No way to select products or order them.
  • Link to desktop site redirects back to the mobile site.
  • "Special deals" link redirects to mobile site homepage.
  • Link to privacy policy goes to illegible desktop page.

If this site was migrated to mobile-first indexing, key pages would be dropped from the index entirely.

The fix: Make your mobile site functionally equivalent to your desktop site. In fact, Enge went so far as to recommend this:

design your mobile site first and other SEO advice

“Design your mobile first first — before you design your desktop site.”

Related Article: What's Inside the Google Search Console Update

3. Your Mobile Blog Navigation Creates Long Crawl Paths

Enge found a travel blog that was missing category pages on its mobile site (i.e., pages that list all of the posts in that category).

To find a post, a crawler would land on the blog homepage. The homepage displayed the most recent five to 10 posts. For older posts, the crawler follows the paginated links at the bottom of the page (e.g., those labeled “2,” “3,” “4,” “>>,” etc.).

Because this travel blog published a lot of posts, Enge found that the oldest post had a crawl depth of 217. In other words, to get to that post, a crawler would need to visit a page, click on the paginated link, visit the next page, click on the paginated link and so on.

length of crawl path a search engine must go through to access older content

Google and other search engine crawlers won’t crawl that deep. Unless they were linked to from pages with a far lower crawl depth, these posts would not be indexed.

The fix: Add blog category pages to the mobile site and otherwise fix issues causing large crawl depths.

4. Your Mobile Site Uses Intrusive Interstitials

“Intrusive interstitial” refers to an offer or prompt that blocks or visually obscures the underlying content. Enge advised session attendees that the use of intrusive interstitials can result in ranking penalties from Google.

According to a post on their Webmaster Central Blog, Google notes, "after January 10, 2017, pages where content is not easily accessible to a user on the transition from the mobile search results may not rank as highly."

The fix: Avoid the use of intrusive interstitials. Visit the Google Webmaster Blog (link above) for examples of intrusive versus acceptable interstitials.

Related Article: Brace for New Mobile Experiences, But Remember Fundamentals

5. Your Mobile Site’s Use of AngularJS or SPA Causes Crawl Issues

Enge reported that sites have seen crawl issues when implementing AngularJS (a popular JavaScript library) and SPA (Single-Page Application).

A guide titled "Get started with dynamic rendering" on the Google Developers site states, "Currently, it's difficult to process JavaScript and not all search engine crawlers are able to process it successfully or immediately."

For sites that rely on JavaScript to render content, the risk is that crawl issues can affect indexing and rankings.

The fix: Google recommends dynamic rendering, which detects visits from crawlers and routes the request to a renderer. According to Google, "Where needed, the dynamic renderer serves a version of the content that's suitable to the crawler, for example, it may serve a static HTML version." Enge referenced as one option sites can use for dynamic rendering.

Change Your Focus to Mobile-First

Over the years, SEOs have focused on a wide variety of approaches: link building, on-page optimization, battling the algorithms, creating great content marketing and more. In 2019, it’s time to drop (just about) everything you’re doing and focus on your site’s mobile experience.

Beyond the five gotchas covered in this article, there’s much more. Follow Google best practices for mobile-first indexing. Make sure your site’s mobile experience is even better than the desktop experience.

Feeling good today? If Google moves you to mobile-first indexing and your site isn’t ready, you’ll be feeling much worse.