Multilingual URLs for language versions

**Is your feature request related to a problem? Please describe.** Currently the different language versions are indicated using a URL parameter, e.g. "?locale=fi". This is not optimal for:

• The user, they generally do not understand what these are and they may remove the relevant information from the URL when they copy-paste it somewhere
• Google, as they say different URLs should be used for different langauge versions: https://support.google.com/webmasters/answer/182192?hl=en
• Marketing, e.g. when you write the service URL to a marketing banner, e.g. "Participate now at meta.decidim.org/es" looks much nicer than "Participate now at meta.decidim.org?locale=es".

We have been also requested that each section could also have different URL names, e.g. "meta.decidim.org/processes" would be "meta.decidim.org/fi/prosessit" in the Finnish version. Some accessibility experts claim that this is even required for accessible services. Pretty standard feature in many CMS systems but this is is completely another problem that boils down to the overall improvement of the CMS features in Decidim:

• Allow defining static page content using the content blocks
• Allow adding multiple same type of content blocks on page
• Possibility to configure the top level navigation
• Possibility to configure the participatory space navigation
• Adding icons to pages and topics

**Describe the solution you'd like** The primary (default) language URLs should be intact as they are now.

The secondary languages should be indicated with a sub-path in the URL, such as "meta.decidim.org/es/...".

Implementing this also requires adding 301 redirections to the old parameter URLs, so that old Google results, social media shares and document links will still point to the correct location. **Describe alternatives you've considered** There are really no alternatives as the suggested is the accepted common "standard" / convention for defining language versions in public web. Common conventions should be followed as that makes the overall experience better for everyone, people and machines. This will also bump the site's SEO relevance.

You can of course add redirections manually for the sub-path URLs simply for marketing purposes but this seems clunky and it's not the right way to go. **Additional context** The URL parameter convention may be acceptable for services which are not facing the public web, i.e. they require logging in from the user.

However, for system such as Decidim, we should follow the commonly accepted convention for public websites as most of Decidim's content is meant to be visible in the public web.

This issue applies to multiple categories (but I can only select one):

• UX / PX / Usability
• Accessibility
• SEO / Search Engine

**Does this issue could impact on users private data?** No.