logging

logging?: false | { fetches?: { fullUrl?: boolean; hmrRefreshes?: boolean }; serverFunctions?: boolean; incomingRequests?: boolean | { ignore: RegExp[] }; browserToTerminal?: boolean | 'warn' | 'error' }

Everything here affects the development terminal only; production builds are untouched. The options divide into four independent streams.

• fetches.fullUrl prints the whole URL of each server-side fetch, so you can see the query string an upstream call actually sent. fetches.hmrRefreshes additionally shows fetches served from the Server Components HMR cache, which are hidden by default.
• serverFunctions is on by default and prints each call as └─ ƒ myAction(arg1, arg2) in 5ms app/actions.ts.
• incomingRequests logs every request; { ignore: [...] } takes regular expressions, which is how you silence a health check that fires every second.
• browserToTerminal forwards console calls from the browser into the terminal with file and line, so you can debug a Client Component without switching to DevTools.

What trips people up

fullUrl prints query strings verbatim — API keys and signed tokens included — into your terminal and any scrollback you share. Server Function logging prints arguments, so a form's field values land in the log too. And logging: false silences the routine dev output, not compile or runtime errors.

import type { NextConfig } from 'next'

const nextConfig: NextConfig = {
  logging: {
    fetches: {
      fullUrl: true,
    },
  },
}

export default nextConfig

import type { NextConfig } from 'next'

const nextConfig: NextConfig = {
  logging: {
    incomingRequests: {
      ignore: [/\/api\/v1\/health/, /\/__probe/],
    },
    serverFunctions: false,
  },
}

export default nextConfig

import type { NextConfig } from 'next'

const nextConfig: NextConfig = {
  logging: {
    browserToTerminal: 'warn',
  },
}

export default nextConfig

import type { NextConfig } from 'next'

const nextConfig: NextConfig = {
  logging: false,
}

export default nextConfig