Server-Timing response headers will pass through to the client

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.

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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:

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

Learn more about the Performance API and Server Timing.