Mobile-first indexing is a method that a search engine uses to prioritize mobile website design over desktop-focused web design. Google has announced it will now be using mobile-first indexing to determine how and why content should be indexed and returned in its web searches. This means that any business owner who has been ignoring mobile considerations won’t be able to any longer.
If a website is optimized only for desktop computers, it is time to make an upgrade to a mobile responsive design. Failure to do so most likely means that the website will get buried further down in Google’s search results. Also, it is expected that other search engines will soon follow Google’s lead.