We've seen great presentations & posts on mobile-first indexing, it's awesome to see all the details (thanks, @aleyda @jenstar @alexisksanders @dawnieando @badams + others)! There are only a few things we've sometimes seen confusion about, so we thought we'd clarify them.
URLs in search: With Mobile-first indexing, we index the mobile version. When we recognize separate mobile URLs, we'll show the mobile URL to mobile users, and the desktop URL to desktop users - the indexed content will be the mobile version in both cases.
Crawled counts: The total number of crawled URLs/day generally won't change, but the balance will shift from mostly-desktop to mostly-mobile crawls. During a switch-over to mobile-first indexing we may temporarily crawl more as we reindex everything.
Cached page: Unfortunately, it looks like we're currently still not showing a cached page for many mobile-first indexed sites. This is a bug, not by design, and should get resolved over time. It's just the UI, it doesn't affect crawling, indexing, or ranking.
Speed and mobile-first indexing: The mobile speed update in July is independent of mobile-first indexing. Fast sites are awesome for users, especially on mobile, since devices & connections there tend to be slower than with desktops.
Mobile website UIs: Using "hamburger-menus" and "accordions" on mobile websites is fine.
On requirements: Neither mobile-friendliness nor a mobile-responsive layout are requirements for mobile-first indexing. Pages without mobile versions still work on mobile, and are usable for indexing. That said, it's about time to move from desktop-only and embrace mobile :)
On ranking: The mobile-first index doesn't change anything for ranking other than that the mobile content is used. While mobile-friendliness is a ranking factor on mobile, being in the mobile-first index is not.
In case you're curious, our docs on mobile-first indexing are at webmasters.googleblog.com/2016/11/mobile… , webmasters.googleblog.com/2018/03/rollin… , developers.google.com/search/mobile-… , and developers.google.com/search/mobile-… for mobile sites in general.
Is there anything we missed? Are there aspects to mobile-first indexing you'd like more information on? Let us know here!
