Google May Combine Similar Language Pages
If you have separate pages with the same language targeting different countries, Google may choose to index one URL but show different titles.
Hreflang For Different Languages is Useful for Brand Searches
If you have websites in completely different languages, hreflang is most useful for brand searches. if Google is already returning the correct pages for different language searches, you probably don’t need to set up hreflang
Don’t Serve Different Language Pages on the Same URL
If you have different language versions of a page that is hosted on a single URL, Google will only index one version.
Google Algorithm Changes Are Applied Universally to All Languages
When Google makes algorithm changes, they try to make them across all sites regardless of differences like language. Exceptions with rich snippets, structured data, knowledge graph, business related information, streaming services can be trickier for legal reasons so they can’t roll updates out all at the same time.
Keep the Markup Language Consistent on a Site
Having the same markup using different markup languages (e.g. JSON-LD and Microdata) can make it difficult for Google to know which one to use.
Google Assigns a Primary Language for Pages with Multiple Languages
The page is less likely to appear for searches for content in secondary languages is less likely to be shown
Google uses Anchor Text Language to Infer Language of the Page
The language used in anchor text of backlinks to your site can be used by Google to infer the language of the page.
Location and Language Don’t Affect Backlinks
The weight of backlinks isn’t affected by the location or language of the website.
Search Console Country Targeting Doesn’t Affect Language
If you target a specific country in search console then you will get a boost local rankings for that location, but it won’t impact searches for same language in a different location.