Google's John Mueller said lesser-used or known languages published on the web are not considered low-quality content just because they are lesser known. He said on Mastodon "good content is good content" no matter what language it is written in.
Daniel Mealo asked, "Does the best recommendation at present become to deindex such pages with to keep from risking the perception that it is low-quality content, even though they are for a legitimate localized target audience?" Should you remove this type of content because there is no support hreflang ISO code for it? The answer is no, according to John Mueller.
John responded, "If this is good content for a niche audience, I would absolutely *not* remove it from indexing. Good content is good content. Your site won't be "penalized" for content in an obscure language." "There's no ISO-639-1 code for ancient Greek, and I wouldn't dare suggest to remove that content from the web," he added.
So what do you do when there is no ISO 639-1 code for the language and you want to use hreflang? You don't use hreflang. John wrote earlier, "If there is no ISO 639-1 code for a language, then there's no hreflang that you can specify there. A hreflang isn't required for a page. It doesn't have to be a part of a hreflang set, there's no ranking advantage if it were."
"The page can have words in any language or script, our systems will try to index it appropriately, and try to show it to users who search for those words. It doesn't matter if there's no ISO 639-1 country code for it," he added.
Forum discussion at Mastodon.
