Mobile-first indexing means that Google uses the mobile version of a website to index and rank its pages. Google fetches that version with the smartphone crawler of Googlebot. Anything that only appears on the desktop version may therefore not count. Google sets out the requirements in Mobile-first indexing best practices.
What does it ask of your website?
According to Google, the mobile and desktop versions should be equivalent on these points:
- the same main content; an accordion or a tab is fine, leaving content out is not;
- the same structured data;
- the same titles and meta descriptions;
- the same meta robots tags.
Example
Say an online shop shows only the first paragraph of a product description on mobile and loads the rest after a tap on “Read more”. Google does not load content that requires user interaction, such as tapping, swiping or typing, so it does not see the rest of the description. If the full text is already in the HTML and only collapses visually, there is no problem.
Common mistake
A noindex or nofollow that only appears on the mobile version, for example because of a separate mobile theme. Google may then fail to index pages even though the desktop version is fine.
How do you check it?
Use URL Inspection in Search Console to see which HTML Google received and compare it with your desktop page. More checks are in the technical SEO checklist.