Google’s John Mueller has confirmed that, starting March 2021, Google will only use mobile crawlers to index web pages. Instead of ‘mobile first’ indexing, it should be called ‘mobile only’ indexing:
It has to be in the (rendered / sstatic) HTML to be indexed.— ? John ? (@JohnMu) October 14, 2020
I'm thinking we should just rename it to "mobile-only indexing" to make it clearer ?
Check your website with a mobile crawler
The website audit tool in SEOprofiler can check your web pages with a mobile web crawler.