"In the meantime, after analyzing the sites that are not yet indexed mobile-first, we've determined that some of these sites are still not ready to be shifted over due to various, unexpected challenges that they're facing. Because of these difficulties, we've decided to leave the timeline open for the last steps of mobile-first indexing. [..]

We currently don't have a specific final date for the move to mobile-first indexing and want to be thoughtful about the remaining bigger steps in that direction."

1. Check the robots meta tags on your mobile pages

Your mobile pages should use the same robots meta tags and your desktop pages. If you mobile pages use noindex or nofollow in the robots meta tag, Google might not be able to index these pages.

2. Check lazy loading web page elements

Google says that you should avoid lazy-loading your primary content based on user interactions (like swiping, clicking, or typing) because Google's web crawler won't trigger these user interactions.

3. Check your robots.txt file

Some websites block mobile URLs in the robots.txt file. If you want to be listed in Google's search results, your robots.txt file should not block your mobile pages. If you block your .css files in your robots.txt file, Google will not be able to render your pages correctly. That can have a negative impact on your Google rankings. You also shouldn't block images.

4. Make sure the content is the same on desktop and mobile

If the mobile version of your website has less content than the desktop version of your website, you should update the mobile version so that it's primary content is the same as on the desktop website. Remember that Google will only use the content of the mobile pages. Use the same clear and meaningful headings on your mobile pages as on your desktop pages.

5. Check images and videos

The resolution of the images on your mobile pages should not be too low and the images should not be too small. Do not use small thumbnails instead of regular images. Google considers thumbnail images low quality. Use meaningful image alt attributes that describe the contents of the images.

"Cross-language canonical is not great. One idea could be to just do hreflang on the homepage, and not do it for the actual content. That would help guide the branded queries to the right version, and assuming the rest are long-tail, they're probably clearer on language anyway."

"The Page Experience Update was a subtle update & won't make or break a site. If you saw a significant drop, it's not from having a slower site. It's easy to sink a lot of time/money into making a faster site, but there could be bigger problems."

"Google's John Mueller said in this past Friday's hangout that in rare situations some sites can get stuck in some sort of algorithmic penalty limbo or black hole state and not be able to recover because Google stopped updating that algorithm. He said this can lead to some sites not being able to recover for several years."

"The cache is not necessarily representative of what's indexed, it's not meant to be used for diagnosing indexing."