Overview
Document language plays a role in Pandoc’s processing of most formats, and controls hyphenation in PDF output when using LaTeX (through babel and polyglossia) or ConTeXt.
Additonally, Quarto, Pandoc, and LaTeX will sometimes generate textual output that requires localization. For example, “Figure” or “List of Figures” for cross references, callout captions like “Note” or “Warning”, or the “Code” caption for folded code chunks.


lang Option
The lang document option identifies the main language of the document using IETF language tags (following the BCP 47 standard), such as en or en-GB. The Language subtag lookup tool can look up or verify these tags.
For example, this document specifies the use of French:
---
title: "My Document"
lang: fr    
---
This will result in the use of French translations as well as the application of other language specific rules to document processing. The following languages currently have full translations available:

English (en, used by default)
Chinese (zh)
Spanish (es)
French (fr)
Japanese (ja)
German (de)
Portuguese (pt)
Russian (ru)
Czech (cs)
Finnish (fi)
Dutch (nl)
Italian (it)
Polish (pl)
Korean (ko)



Alternate Language
If you aren’t happy with the default language used for a given part of a document you can provide alternate language via the language key (this can be used at a document or project level). For example, to override the values for the “Author” and “Published” captions used within title blocks you could do this:
---
title: "My Document"
author: "Norah Jones"
date: 5/22/2022
language: 
  title-block-author-single: "Writer"
  title-block-published: "Updated"
---
As described below, you can also provide these translations in a standalone YAML file and reference it as follows:
---
title: "My Document"
author: "Norah Jones"
date: 5/22/2022
language: custom.yml
---
You can discover all of the language values that can be customized by referencing this file: https://github.com/quarto-dev/quarto-cli/blob/main/src/resources/language/_language.yml.

Per-Language Alternates
Alternate values can be restricted to a particular target language using subkeys of the language key. This way, distinct values can be defined for each language. For example, you can override the English and French versions of the “Published” caption:
---
title: "My Document"
author: "Norah Jones"
date: 5/22/2022
lang: fr
language:
  en:
    title-block-published: "Updated"
  fr:
    title-block-published: "Mis à jour"
---
In this case the French “Mis à jour” will be used since lang is set to fr.
These language-specific alternate values can also be provided in a standalone YAML file. For example, the following file could be used by setting language: custom.yml in the metadata:


custom-language.yml

en:
  title-block-published: "Updated"
fr:
  title-block-published: "Mis à jour"




Custom Translations
You can create and use a custom translation for a new language not supported by Quarto as follows:

Make a copy of the default _language.yml file (https://github.com/quarto-dev/quarto-cli/blob/main/src/resources/language/_language.yml).
Provide translations from the default English values.
Specify the custom translation file using the language option. For example:
---
language: custom.yml
---

The language option can be specified at a project or document level. Additionally, if you include a _language.yml file in the root of your project alongside your _quarto.yml config file it will be automatically used.
If you create a language translation file please consider contributing it so others can benefit from it. See the documentation on contributing language translations for additional details.