CONFIRMED
Mobile-first indexing is mandatory
MOBILE
HIGH Impact
INTERMEDIATE
The Myth
"Google primarily uses the mobile version of content for indexing and ranking."
The Truth
TRUE - Mobile-first indexing is now the default for all websites. Google crawls and indexes the mobile version of your site first. If your mobile site has less content than desktop, that's what Google sees. Responsive design is the recommended approach. Sites without mobile versions may have issues being properly indexed.
DInsight from @dejanseo
"If your mobile experience is broken, your rankings will suffer. Period. Most users are on mobile—build for them first."