{
  "slug": "emulate-device-viewport-and-user-agent-f91aff788a2d",
  "title": "Emulate device viewport and user agent",
  "tools": [
    "chrome-devtools-mcp"
  ],
  "tags": [
    "agent"
  ],
  "introduced_at": "2026-01-27T13:20:22.000Z",
  "announced_at": "2026-01-27T13:20:22.000Z",
  "effective_at": null,
  "date_basis": "source-publication",
  "status": "unknown",
  "how": {
    "incantation": "When checking a page under a mobile or different desktop device configuration, call `emulate` with `viewport` and/or `userAgent`; set either to null to reset its override.",
    "examples": [
      "emulate({\"viewport\": <viewport-value>, \"userAgent\": <user-agent-string>})"
    ],
    "gotchas": [
      "Version: 0.14.0",
      "viewport: Viewport override; set to null to reset to the default viewport. Its value format is not specified in this version's docs.",
      "userAgent: User-agent override; set to null to clear it.",
      "Both attributes are optional.",
      "The recommended way is to emulate via the MCP server instead of a parallel DevTools session.",
      "Docs conflict: Current official docs describe viewport as a formatted string and clearing userAgent with an empty string; the version 0.14.0 docs instead specify unknown value types and null resets. This card follows the 0.14.0 behavior."
    ]
  },
  "why_it_matters": "Check a web page under a mobile or different desktop device configuration.",
  "sources": [
    "https://github.com/ChromeDevTools/chrome-devtools-mcp/releases/tag/chrome-devtools-mcp-v0.14.0",
    "https://github.com/ChromeDevTools/chrome-devtools-mcp/pull/798",
    "https://github.com/ChromeDevTools/chrome-devtools-mcp/blob/a8169676f920f88965a2574f53affe15c1278b43/docs/tool-reference.md"
  ],
  "rank": 0.96046,
  "judge": {
    "publish": true,
    "judge_model": "codex-cli/gpt-6-luna+typesafe/jev-1.13.0",
    "prompt_version": "extract-v7+enrich-v1+judge-v2x3+jev-publish-v1"
  },
  "review_state": "approved",
  "provenance": {
    "run_id": "ghtools-20261008",
    "verdict_id": "ghtools-20261008:ghtools-20261008-5dba2f3d6314e1b3-4:gate",
    "evidence_hash": "8a95a0b2b33db9003b3286ddb08fe888c98236147fa4f92a83f17c2716e8e63f"
  },
  "review": {
    "draft_hash": "59e416aa39c5d792821eb236c0c7e328aa68f8bc76f320e455d9eea604501196",
    "reviewer": "publication-gate",
    "reviewed_at": "2026-10-07T00:00:00.000Z",
    "decision": "ghtools-20261008:gate",
    "reason": "3 of 3 judge runs approved with p_yes >= 0.9 (mean 0.96 >= 0.9; 2 needed) and Jev gave 0.81 (>= 0.6 needed)."
  }
}