As Google rolls out Mobile-First indexing, it is also trying to clear confusions that are arising. So they tweeted to clarify some points.
URLs in Search: If you have different URL versions for mobile and desktop, Google will show mobile version to the mobile visitors and desktop version to the the desktop visitors. However in both cases mobile version will be indexed.
Crawled Accounts: Number of crawled URLs per day won’t really changes, but there will be a shift from mostly desktop to mostly mobile. While switching to mobile-first indexing, Google may temporarily crawl more for reindexing.
Cached Page: Google is still not showing a cached page for many mobile-first indexed sites. This is a bug that will be resolved over a period of time and doesn’t affect crawling, indexing or ranking.
Speed and Mobile-First Indexing: Mobile-first indexing and mobile speed update to come in July are independent. Though you should make your sites fast, especially for mobile users.
Mobile Website UIs: Google says it’s fine to use “hamburger-menus” or “accordions” to make content less overwhelming.
On Requirements: It’s not necessary to have a mobile-friendly or mobile-responsive layout for mobile-first indexing. Desktop versions are usable for indexing.
On Ranking: Mobile-first indexing doesn’t affect ranking. Mobile friendliness is a ranking factor on mobile, but not being in the mobile-first index.
Documents: Check out the docs on mobile-first indexing.
