Mobile-first indexing means Google primarily uses the mobile version of your page for indexing and ranking, so the practical answer is that your mobile version is what counts, and any content or link that exists only on desktop can effectively be ignored. It does not mean Google throws away your desktop site or refuses to look at it, but it does mean the mobile rendering is the one driving your results, and that shifts where the risk lives.

The reason this matters comes down to parity. For years many sites served a trimmed-down mobile experience, hiding sections, collapsing text, or dropping internal links to fit a small screen. Under mobile-first indexing, that trimming has teeth: if a paragraph, an image, or a link to another page appears on your desktop layout but is absent from the mobile version Google crawls, it can be treated as if it does not exist for indexing purposes. The content you assumed was working for you is not in the version that counts. This is the desktop-only-content risk, and it is the single most common way mobile-first indexing quietly costs sites.

So the verdict is not that desktop is irrelevant, but that desktop-only content is at risk. Anything you depend on for ranking, your main copy, your structured data, your internal links, and your important images, needs to be present in the mobile version, not just the desktop one. This reflects observed behavior rather than a fixed rule, so treat the specifics as worth confirming against current guidance, but the direction has held steadily: build for content parity and the mobile-first shift is a non-issue.

To act on this, open your key pages on a real mobile rendering, not just a narrowed desktop window, and compare them against the desktop layout. Confirm that every piece of important content and every internal link present on desktop is also present on mobile. Where you find desktop-only content, surface it on mobile too, so the version Google actually indexes carries everything you are counting on.