Hreflang
Hreflang is an HTML tag telling search engines that a page has alternate-language versions — and which URLs correspond to which language and region.
Hreflang is a link rel='alternate' hreflang tag in a page's head (or in sitemap.xml). It helps Google show the right language version to users and prevents duplicate-content issues on multilingual sites.
On Ecosta's site, FI is x-default (root) and EN lives at /en/ — both pages must point to each other via hreflang, otherwise Google may treat them as duplicates.
