Configuration (vercel.json)

The vercel.json project configuration file — build settings, rewrites, redirects, headers, function config, and crons.

Most projects deploy with zero configuration because Vercel detects your framework. When you need to override defaults, you add a vercel.json file at the root of your project. Settings defined in the dashboard and in vercel.json are merged; vercel.json is version-controlled, which makes it the better place for anything you want reviewed alongside code.

A representative example

{
  "buildCommand": "next build",
  "outputDirectory": ".next",
  "framework": "nextjs",
  "redirects": [
    { "source": "/old", "destination": "/new", "permanent": true }
  ],
  "rewrites": [
    { "source": "/api/:path*", "destination": "https://backend.example.com/:path*" }
  ],
  "headers": [
    {
      "source": "/(.*)",
      "headers": [
        { "key": "X-Frame-Options", "value": "DENY" }
      ]
    }
  ],
  "functions": {
    "api/heavy.ts": { "memory": 3008, "maxDuration": 60 }
  },
  "crons": [
    { "path": "/api/cron/cleanup", "schedule": "0 3 * * *" }
  ]
}

Common fields

Field	What it does
`buildCommand`	Override the detected build command
`outputDirectory`	Where build artifacts are written
`installCommand`	Override how dependencies are installed
`framework`	Force a framework preset
`redirects`	Server-side redirects (301/302 via `permanent`)
`rewrites`	Proxy a path to another path or external URL without changing the URL
`headers`	Attach response headers by path pattern
`functions`	Per-function memory, `maxDuration`, and runtime settings
`crons`	Scheduled function invocations
`regions`	Which region(s) functions run in

Redirects vs rewrites

A redirect sends the browser to a new URL (the address bar changes).
A rewrite serves content from a different path or origin while the URL stays the same — useful for proxying an API or composing apps.

Function configuration

The functions object tunes individual functions — for example raising memory or maxDuration for a heavy endpoint. To enable Fluid Compute for specific environments programmatically, use the fluid property.

Precedence and validation

vercel.json settings generally take precedence over dashboard settings where they overlap.
The CLI validates the file during vercel build / vercel deploy; a malformed vercel.json fails the build with an error.
vercel pull brings the effective project settings down into .vercel/ so local vercel dev / vercel build match the cloud.