Turbopack Docker build significantly slower than Webpack (~6.8x)

[hmaesta]

When running npm run build natively with Turbopack, the build time is significantly faster compared to Webpack (~1s vs. ~10s); however, the opposite occurs when building a Docker image.
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Link to the code that reproduces this issue

https://github.com/hmaesta/nextjs-turbopack-docker
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To Reproduce

You can reproduce by cloning this repository or following these steps with create-next-app:

1. Initiate a minimal project

npx create-next-app@latest docker-experiment \
  --js --no-tailwind --no-react-compiler --no-linter \
  --empty --use-npm --src-dir --app --import-alias "@/*"

^{(As of Jan 6 2026, using "canary" instead of "latest" presented similar results)}

2. Go to the project

cd docker-experiment

3. Create a minimal Dockerfile

curl -fsSL "https://raw.githubusercontent.com/hmaesta/nextjs-turbopack-docker/refs/heads/main/Dockerfile" -o Dockerfile

^{... or copy the contents of Dockerfile}

4. Add output: 'standalone' to Next config

perl -i -pe 'print "  output: \x27standalone\x27,\n" if $. == 3' next.config.mjs

^{... or edit next.config.mjs manually}

5. Build the image using Turbopack

docker build . -t docker-experiment-turbopack

Using a M2 Pro MacBook, the npm run build step took ~76s. (Docker is set to max cores and memory.)

Out of curiosity, running time npm run build natively - outside of the Docker context - takes less than 2s.

6. Move to Webpack

Now, let's move to Webpack by adding --webpack to package.json commands:

perl -i -pe '
  s/"dev":\s*"next dev"/"dev": "next dev --webpack"/;
  s/"build":\s*"next build"/"build": "next build --webpack"/;
' package.json

^{... or edit package.json manually}

7. Build the image using Webpack

docker build . -t docker-experiment-webpack

This step takes ~11s.

Running time npm run build natively takes almost 10s; really close to the Docker results.

In a large codebase, these results are exponential in scale. In my daily job, Webpack takes ~90 seconds, compared to ~1,000 seconds (16 minutes) with Turbopack.

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Current vs. Expected behavior

• The build step shouldn't be so slow compared to the time it takes to run natively (without Docker)
• Ideally, it should be faster than Webpack

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Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 24.6.0: Mon Aug 11 21:16:34 PDT 2025; root:xnu-11417.140.69.701.11~1/RELEASE_ARM64_T6020
  Available memory (MB): 32768
  Available CPU cores: 12
Binaries:
  Node: 25.2.1
  npm: 11.7.0
  Yarn: 1.22.22
  pnpm: 10.18.2
Relevant Packages:
  next: 16.1.0 // ← This is incorrect; I have "16.1.1" in my package.json
  eslint-config-next: N/A
  react: 19.2.3
  react-dom: 19.2.3
  typescript: 5.8.3
Next.js Config:
  output: standalone

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Which area(s) are affected? (Select all that apply)

Turbopack

Which stage(s) are affected? (Select all that apply)

next build (local)

Additional context

The same issue has also been reported by #77721 (comment)

Maybe related to #77624 and #82625

[mischnic]

I can reproduce this, but I don't really understand yet why this is happening. Especially weird given that it's not "slow CPU" per se, given that Webpack doesn't get slower.