@json-translate/check compares translated JSON locale files against a source locale. It is designed for the last step after translation: the point where a developer wants to know whether a translated file can safely enter a build.

• It fails when a target file cannot be parsed as JSON.
• It reports keys that exist in the source but are missing from the translation.
• It reports extra keys that appeared in the translated file.
• It compares placeholder tokens such as {name}, {{count}}, ${value}, and %s.

You do not need a project dependency to try it. Run the checker against one source file and one or more target files:

npx @json-translate/check --source locales/en.json --target locales/fr.json --target locales/de.json

If the French locale lost a key, added an obsolete key, and dropped a runtime placeholder, the output looks like this:

FAIL locales/fr.json
  missing key: nav.save
  extra key: legacy.banner
  placeholder missing at greeting: {name}

Use JSON Translate to create draft translations, then run the CLI before merge. The CLI is intentionally narrow: it does not judge translation quality, tone, or grammar. It checks the file-level mistakes that are easiest to automate.

• View @json-translate/check on npm
• Use JSON Translate Check in GitHub Actions
• Read the JSON Translate CLI page
• Translate i18next JSON files online