There are many ways through which one can set a website to multiple languages. One of the strategies applied is using a single URL for all the languages and creating sub-directories for each language. Sub domains are also useful when you want to have different languages for your website. You can have country-specific domains for each of the languages you intend to use on your website. However, there are websites that were initially designed without multi-languages in mind but their owners would like to expand to more languages.
Google has responded to this question in a bid to help those who had not initially integrated different languages in their websites. Google offers search results based on the language used, so if your website is set to a specific language, the Google server will easily index the information you have shared. On this note, Google has advised website owners to consider creating multi-lingual pages that define the language for each URL.
For instance, if you own (www.example.com) and the page is set to English but you would like to create some content in Spanish, you are better off creating a utilising a different domain (www.example.es). Otherwise, you should include a translator to the text if you intend to keep all the pages the same.
Setting the pages to read a specific language helps Google to recognise search queries and redirect people to the information you have shared. Google will also find it challenging to distinguish which language the website is ranking for if there are no definite pages for different languages. Therefore, if the pages do not have a definite language, this will injure the overall ranking of the website on search engines.
The main question people are trying to answer is whether to use separate domains or to keep all the content on one domain. You do not necessarily need to put the content on separate domains, but you can use sub-directories and sub-domains for each language.
It is also necessary to understand that the Google hreflang guidelines do not state that one must use multi-URLs. You will observe cases where a server offers the wrong language content accidentally (for instance Spanish instead of English), and it can also prove difficult to find the correct version.
Some sites only translate a small part of the content, with the biggest part remaining in a language you do not understand. With multiple URLs for different languages, it is easier to identify hreflang and crawl errors. Such errors can prove difficult to diagnose on a single URL and there are also chances the server could set serving up your various languages incorrectly.