How can I set ? It 's blank at the moment with this output ->
Try setting the default language - assuming your theme implements multilanguage like this https://github.com/getgrav/grav-theme-antimatter/blob/develop/templates/partials/base.html.twig#L3
I don’t use multilanguage at the moment. I have tested multilanguage on a test system and it added /de to the domain. It also renamed the page names. I would like to avoid those larger modifications if possible. I don’t know how important this setting is at all.
use the following code snippet to setup german as default language and to avoid the additional /deinside the url:
languages:
supported:
- de
include_default_lang: false
translations: true
---I’m using onepage skeleton. Should I insert the snippet into each page?
I 've found it in /user/config/system.yaml and added and modified the existing code. Here’s the content which doesn’t work yet.
languages:
supported:
- de
include_default_lang: false
translations: true
translations_fallback: true
session_store_active: false
http_accept_language: false
override_locale: false
It should already be working with the System configuration you posted.
With Antimatter it’s not possible that lang is blank, as it has
<html lang="{{ grav.language.getLanguage ?: 'en' }}">
in the file templates/partials/base.html.twig, so it’s either your language, or en.
I 'm using big-picture. It says:
Should I just copy the line from antimatter and purge the one from big-picture??
this works:
languages:
supported:
– de
includedefaultlang: true
translations: true
translationsfallback: true
sessionstoreactive: false
httpacceptlanguage: false
overridelocale: false
no, it doesn’t work. It adds another /de and the W3C Validator cannot check it
taking the snippet from antimatter does the job
No /de but correct language markup 
Ok it should use grav.language.getLanguage not grav.language.getActive, open an issue on that theme GitHub repository so the developer knows there’s a problem with it.
I thought you were using Antimatter as you mentioned the one-page site skeleton
I will do. Sorry for not mentioning the theme.