---
title: "How it works"
date: 2026-09-12
author: "Claude MCP"
---

# How it works

Domain per Language sits between the domain a visitor arrives on and Joomla's own multilingual routing. This article describes what it does with a request, with a link, and with the tags search engines read.

 
## The language comes from the domain

 On a configured domain the plugin sets the language of the request before the language filter runs. That order matters: without it, Joomla would pick the language from a cookie, the session or the browser, and a visitor who once chose Dutch would keep seeing Dutch on your English domain.

 A page in that language is then served without its language code. A language that has no domain of its own keeps its code and is served on the domain of the default site language.

 
## Redirects

 All of these are permanent redirects (301), and none of them happen on a POST request:

 
- `www.example.com/en/about` on the English domain becomes `www.example.com/about` - the language code of the domain's own language is duplicate content.
- A page in another language moves to the domain of that language, so `www.example.com/nl/over-ons` becomes `www.example.nl/over-ons`.
- The www or bare variant of a configured domain moves to the configured one, keeping path and query.

 A host that is not configured is left completely alone. Your staging domain, `localhost` or an IP address therefore behaves like an ordinary multilingual Joomla site, with language codes in the URL.

 
## Links between domains

 Joomla builds links with its own router, which always keeps the host of the current request. A link to another language therefore leaves the router with a marker in its path, and the plugin turns that marker into a real absolute URL before the page reaches the visitor. You never see it; what you get is `https://www.example.nl/over-ons` in the menu, in the language switcher, in hreflang and in feeds.

 Three layers make sure a marker never reaches a visitor: the rewrite of the finished page, a redirect for a marker URL that arrives anyway (for example from an e-mail sent by a scheduled task), and a public method other extensions can call. See the article about links in other extensions.

 
## hreflang, x-default and the canonical

 The alternate links that the language filter adds are rewritten to the domain of each language, x-default included, so search engines see one clean set of URLs per page.

 The core **System - SEF** plugin has a *Site Domain* field. When it is filled in, that plugin puts the canonical of every page on that single domain, which is wrong as soon as a page lives on another language domain. Domain per Language moves such a canonical back to the domain of the page's language; only the host changes. On a host that is not configured, the behaviour of the SEF plugin is left untouched.

 
## Caching

 The plugin finishes its work before a page is stored in the cache, so a cached page already carries the right URLs. Joomla caches per full URL including the host, so each domain has its own cache entries.