I'm making infotainment platform on three languages (ru, en, he) with targeting on the Israeli market (multilingual people). Perhaps in the future - a social network. How indicate to robots (like Google), website in the three languages?
The main problem: Robots don't tell you language they are requesting page in. My application written on Java, and for get a page in one of 3 (ru, en, he), before HTML, I am doing request getLocale().getISO3Language(); But robots ignore this parameter, and by default all pages only on English. On the page "feed" can be messages on three languages, and I don't want to promotion some a one. How indicate to robots, website in the three languages?
You can indicate to search engines that your website supports multiple languages, with hreflang attribute in your HTML. This attribute tells search engines about the different language versions of a page, which helps them serve the correct language version to users based on their preferences.
In your case you can use hreflang like this:
<link rel="alternate" href="https://www.yoursite.com/en/page" hreflang="en" />
<link rel="alternate" href="https://www.yoursite.com/ru/page" hreflang="ru" />
<link rel="alternate" href="https://www.yoursite.com/he/page" hreflang="he" />
Also, keep in mind that each language version of your page has a canonical tag pointing to itself to prevent duplicate content issues.