On August 10, 2026, Vercel's CDN will stop stripping the Server-Timing response header and begin passing it through to the client.

Use Server-Timing to report backend metrics like database query time and cache hits. These values appear in the browser's network panel and as PerformanceServerTiming entries through the Performance API.

Server-Timing: db;desc="Database";dur=53,cache;desc="Cache";dur=4.2

If you want to keep the current behavior, where the header is stripped from every response, you can add a transform in vercel.json:

{
  "$schema": "https://openapi.vercel.sh/vercel.json",
  "routes": [
    {
      "src": "/(.*)",
      "transforms": [
        {
          "type": "response.headers",
          "op": "delete",
          "target": {
            "key": "server-timing"
          }
        }
      ]
    }
  ]
}

Learn more about the Performance API and Server Timing.