URLs

URLs get a language prefix automatically, and reading the active language is also automatic.

Function	Without multilang	Under /es/
get_permalink($id)	https://site.com/blog/foo/	https://site.com/es/blog/foo/
home_url('/about/')	https://site.com/about/	https://site.com/es/about/
wp_nav_menu (links)	native	prefixed with /es/

System URLs (wp-admin, REST, feeds, sitemap) are excluded automatically. The site root (/) redirects to /{default-language}/.