If you use hreflang on any of your pages, you might want to double check Google Search Console for errors.  Many webmasters received “Errors in hreflang” emails from Google yesterday, even for sites/pages that previously passed.

You can check for messages from Google, or you can also check the “International Targeting” section in Google Search Console for any hreflang implementation errors on your sites.

Marie Haynes shared the email she received from Google.

This isn’t a new error itself, but many webmasters have just received them for the first time, even with previous hreflang implementations.

Google has both a support section and a support video for those implementing hreflang, which explains both how it works and how to correctly add it to pages.  The most common errors are incorrectly implementing country or language codes, or not including tags on all the pages properly,

Important: Make sure that your provided hreflang value is actually valid. Take special care in regard to the two most common mistakes:

• Missing confirmation links: If page A links to page B, page B must link back to page A. If this is not the case for all pages that use hreflang annotations, those annotations may be ignored or not interpreted correctly.
• Incorrect language codes: Make sure that all language codes you use identify the language (in ISO 639-1 format) and optionally the region (in ISO 3166-1 Alpha 2 format) of an alternate URL. Specifying the region alone is not valid.

So if you are using hreflang, even if there were no previous issues with the implementation, you will want to double check it to make sure there are no new errors popping up, and if there are, to fix them.