It kind of depends what you mean by build. From scratch - I have no idea. For Google Chrome? It's just an API call away - https://cloud.google.com/translate/doc

It kind of depends what you mean by build. From scratch - I have no idea. For Google Chrome? It's just an API call away - https://cloud.google.com/translate/docs/basic/detecting-language https://cloud.google.com/translate/docs/basic/detecting-lang...