Polylang

1. Set up your languages in Languages → Languages.
2. Tick the same languages on the Languages tab and choose the same default language.
3. Add the switcher, and remove Polylang’s Language switcher widget or menu item if you used one.

On each page, the plugin uses Polylang’s list of translations. When a page has no translation, Polylang links to that language’s home page. Works with directories, subdomains and a domain per language.