Underestimate useful hreflang x-default value
First What is Hreflang?
hreflang with a value hreflang=”fr-fr” for example is used to indicate for what language the page is
According to Gary Illyes from Google there are so many hidden advantages to use the hreflang x-default value from hreflang that is underused
X-default from Hreflang is an Underused value
This value indicate that a page does not have a specific country code or language. it basically means that all user are send back there by default if the page does not specify any country or value
Use to send back user to a page that doesn’t target any particular country or language, x-default from hreflang offer many useful case such has discovering new url and conversion
gary explained in a post on Google Search Central what he noticed about hreflang attribute and specifically the x-default value.
Typically if an user is on a website that has a hreflang tag, if the website has a spanish, english and Italian version, if the english is referred with x-default value on the hreflang then if Belgium people for instance use the website they will be send to the english page because it has the x-default value.
Promote discovery of new URLs for robots
In addition to being used to drive users to a specific language based on their language, Hreflang with x-default value also allows users to discover new urls. This can be really useful for big website structured to ensure that every localized URL on the website is properly link
like Gary Illys give an exemple:
<link rel="alternate" href="https://example.com/en-us" hreflang="en-us" />
<link rel="alternate" href="https://example.com/country-selector" hreflang="x-default" />
Increase Conversion
Your goal with a website and content is that users read it whatever their language is. For that matter if you have created a content on your website in a specific language but you want user from another language to still be able to access it and read it, then you can use the x-default from hreflang in that matter
like for example:
<link rel="alternate" href="https://example.com/fr/journal personel" hreflang="fr" />
<link rel="alternate" href="https://example.com/lang-selector" hreflang="x-default" />