Content Language Tags
Certain search engines, such as Bing, do not support the
rel="alternate" hreflang="x" annotations. There are three methods that can be used to help these search engines determine which language is being targeted.
HTML meta element
<head> section of the page, add a
<meta> element with the
http-equiv="content-language" attribute that specifies the language of the page.
<head> <meta http-equiv="content-language" content="en-us" /> </head>
Note that this meta tag is reported as deprecated but Bing still looks at this signal to understand the language and the targeted audience of a web page. Therefore it is still a good idea to implement it in the
<head> section of each page on the site with the appropriate language-locale code.
HTTP response header
An HTTP header can be used to indicate the language of a page for host-wide location tagging or non-HTML document such as PDFs.
HTTP/1.1 200 OK Content-Language: en-us
<html> tag language attribute
A language attribute on the
<html> tag (lang and/or xml:lang) should be used to declare the default language of the actual text in the page, as such:
<html lang="en-us"> ... </html>
hreflang tags help indicate Google and Yandex in what language the content of a page is written and what audience (region) this content is targeting. This allows those search engines to serve the right content to the right user.