Your own language from the panel

Three steps

1. Add the language. A code of 2–3 lowercase Latin letters (fr, de, pt-br), the name in English and in the language itself, the writing direction and the plural rule. The code cannot be changed later: it appears in addresses and records. Codes taken by the package and reserved words are rejected.
2. Download the sample and translate. The file nex1on-<code>.json contains all interface keys (the core and the enabled modules) with the English text:

{
  "_meta": { "format": 1, "language": "fr", "base": "en", "keys": 5800 },
  "strings": { "admin.save": "Save", "news::post.title": "Title" }
}

Translate the values only. Keep two things: the {placeholders} ({name}, {count}) and the number of plural forms in texts with a number (for example, “{count} file|{count} files”: as many forms as the language rule has, that many variants separated by “|”).

1. Upload, check, turn on. The file is checked line by line. What is accepted is saved, and an upload adds to the previous one, so you can translate in parts. If something is missing, the “Download only what is missing” button gives you a file with the missing keys.

What is checked (protection)

Rejected lines are listed with the reason (the first 100); they do not go into the translation file and are shown in English. An empty value means “not translated”.

Completeness and turning on

The language page shows the share translated. A full translation (100%) is turned on at once. From 90% — with an explicit checkbox: what is missing is shown in English. Below 90% it cannot be turned on. A language that is on appears in the site’s language picker and in the panel language of every person; “Hide on the site” removes it for visitors, while the panel keeps speaking it. New modules and updates add keys, so completeness drops, and what is missing can again be downloaded as a separate file.

Where translations live and what happens on update

Translations live in storage/languages/<code>/core.json and <module>.json; the language registry is in the languages.custom setting. An engine update does not touch these files, and the shipped files (locales/*.json) stay as they are. Deleting a language first requires turning it off and moves its files to storage/languages/_trash/ next to them instead of erasing them; records written in that language keep their text. Your own edits of individual words are still made in “Interface texts”.