axe-core/lib/checks/language/valid-lang.json

Accessibility engine for automated Web UI testing

{
  "id": "valid-lang",
  "evaluate": "valid-lang.js",
  "metadata": {
    "impact": "serious",
    "messages": {
      "pass": "Value of lang attribute is included in the list of valid languages",
      "fail": "Value of lang attribute not included in the list of valid languages"
    }
  }
}