Though Gary Illyes, a Google analyst, believes that search engines like google and yahoo might depend less on hreflang and a lot more on automatic language detection Down the road, for now, the tag is our best guess.  If none of they're used, Google will trust in other signals like https://captainbookmark.com/story18754189/the-smart-trick-of-%D0%90%D0%B2%D1%82%D0%BE%D0%BC%D0%B0%D1%82%D0%B8%D1%87%D0%B5%D1%81%D0%BA%D0%B8%D0%B5-%D1%82%D0%B5%D0%B3%D0%B8-hreflang-%D0%B8-%D0%BA%D0%B0%D0%BD%D0%BE%D0%BD%D0%B8%D1%87%D0%B5%D1%81%D0%BA%D0%B8%D0%B5-%D1%82%D0%B5%D0%B3%D0%B8-seo-that-no-one-is-discussing