diff --git a/docs/i18n_languages.md b/docs/i18n_languages.md
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--- a/docs/i18n_languages.md
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@@ -1,10 +1,25 @@
 # I18N Guidelines
 
-In JSON file:
+[react-i18next](https://react.i18next.com/) is the framework used for internationalization.
+
+## Locales
+
+Locales are in folder `./src/i18n/locales`, one folder per language.
+
+A single JSON file represents a namespace (group of translation).
+It's a key/value structure.
+
+Please:
 
 - Keep the file sorted
-- Always write in lowercase
+- First letter of each value is lowercase
 
-In GUI:
+Translation in GUI:
 
-- If the first letter of the translation must be uppercase, use the postProcess, for example: `{t_auth('advanced_users', { postProcess: 'capitalizeFirst' })}`
+- If the first letter of the translation must be uppercase, use the postProcess, for example: `t('core:advanced_users', { postProcess: 'capitalizeFirst' })`
+- For all translation in uppercase `{ postProcess: 'capitalizeAll' }`
+- See `.src/i18n/i18n.ts` for processor definition
+
+## Missing language?
+
+- Please open an issue on the project's github repository and specify the missing language