
![Turbopack image](Screenshot-2026-05-15-at-4.15.03-PM.webp)

_package-lock.json, which locks the exact versions of dependencies and their
sub-dependencies for a project using the Node Package Manager (npm), ensuring
consistent installations across different environments_

## Table of Contents

- [What is Turbopack?](#what-is-turbopack)
- [Some key features of Turbopack](#some-key-features-of-turbopack)
    - [Performance enhancement](#performance-enhancement)
    - [New functionalities](#new-functionalities)
    - [Subresource integrity support (SRI) feature](#subresource-integrity-support-sri-feature)
- [The "Next.js inferred your workspace root" warning explained](#the-nextjs-inferred-your-workspace-root-warning-explained)
- [How to fix the "Next.js inferred your workspace root" warning](#how-to-fix-the-nextjs-inferred-your-workspace-root-warning)
- [Why paying close attention to output returned to Terminal during development is so important and how to make the process easier](#why-paying-close-attention-to-output-returned-to-terminal-during-development-is-so-important-and-how-to-make-the-process-easier)
- [Key takeaways](#key-takeaways)
- [Related Resources](#related-resources)

Sometimes, when running `npm run dev`, the following warning may be returned in
Terminal:

```shell
fullstack-blog@0.1.0 dev
> next dev

▲ Next.js 16.2.6 (Turbopack)
- Local:         http://localhost:3000
- Network:       http://192.168.1.163:3000
✓ Ready in 275ms
⚠ Warning: Next.js inferred your workspace root, but it may not be correct.
 We detected multiple lockfiles and selected the directory of /Users/mariacam/package-lock.json as the root directory.
 To silence this warning, set `turbopack.root` in your Next.js config, or consider removing one of the lockfiles if it's not needed.
   See https://nextjs.org/docs/app/api-reference/config/next-config-js/turbopack#root-directory for more information.
 Detected additional lockfiles:
   * /Users/mariacam/Development/nextjs-fullstack-blog/package-lock.json
```

The warning indicates that a straggling `package-lock.json` resides in the home
directory. For those of us coming from using Webpack with Next.js, in order to
understand this warning, we first have to understand what Turbopack is and what
it does.

## What is Turbopack?

Turbopack is a Rust-based bundler introduced and integrated into Next.js 16,
specifically designed to enhance the development experience for JavaScript and
TypeScript applications. It serves as the Next.js 16+ default bundler, replacing
Webpack.

## Some key features of Turbopack

### Performance enhancement

- **Using Turbopack means faster builds**: Production builds with Turbopack are
  two times to five times faster compared to Webpack.
- **Using Turbopack means improved refresh times**: Development with Turbopack
  means up to 10 times faster refresh times during development. This means
  developers can view changes almost immediately.

### New functionalities

- **File system caching**: Turbopack stores compiler artifacts on disk, which
  reduces compile times significantly, especially for larger projects. Storing
  compiler artifacts on disk means you can enable disk caching in your
  development environment, which allows artifacts to persist between sessions.
  This is meant to improve performance during subsequent compilations. This can
  significantly reduce compilation times within large projects.
- **Efficient server-side hot reloading**: Turbopack optimizes the reloading
  process by only refreshing changed modules, which in turn improves development
  efficiency.

### Subresource integrity support (SRI) feature

Subresource integrity support (SRI) means that browsers can verify that
JavaScript files have not been altered during transit. This feature enhances
security by ensuring that only approved scripts are executed, preventing
potential attacks from compromised or suspicious resources. It verifies file
integrity by generating cryptographic hashes for JavaScript files, thereby
enhancing application security.

## The "Next.js inferred your workspace root" warning explained

So what does the "Next.js inferred your workspace root" warning mean and why is
it important to understand? It means that Turbopack selected the wrong
`package-lock.json` for the Next.js Fullstack Blog application. It also detected
the right one inside the nextjs-fullstack-blog directory, but did not select it.
That is potentially very bad, especially if you don't pay attention to warnings
rendered in the Terminal console while running the `next dev` script or the
`next build` script for that matter.

Using the wrong `package-lock.json` in an application can wreak all sorts of
havoc in development. And even worse (as in this case), using the wrong
package.json can wreak even more havoc!

## How to fix the "Next.js inferred your workspace root" warning

Fixing the "Next.js inferred your workspace root" warning is simple. In the
instance displayed here, just `rm package.json` and/or `rm package-lock.json`
from the home directory. However, make sure that you have changed into the
directory where the straggling `package-lock.json` or `package.json` file
resides, otherwise you might end up removing your application's (correct)
`package.json` or `package-lock.json` file.

One way of making sure you are in the correct directory is to run the following
command in Terminal:

```shell
pwd
```

The `pwd` command returns the path to the directory you are currently in.

In the case here, if you are inside the root directory of your Next.js
application, something like the following should be returned in Terminal:

```shell
/Users/mariacam/development/nextjs-fullstack-blog
```

However, perhaps you are not actually at the root of
`/Users/mariacam/development/nextjs-fullstack-blog`. Perhaps you changed into
your home directory (~) for whatever reason, and forgot. Before running
`npm install`, you should double check the directory you are in by running the
`pwd` command.

If you run `pwd` and you are not at the root of your Next.js application but at
the root of your home directory, the following would be returned:

```shell
/Users/mariacam
```

By checking which directory you are actually in before running 'npm install',
you avoid creating a(nother) `package-lock.json`, thereby causing Turbopack to
detect `multiple lockfiles` and potentially select the wrong one to use in
development. This potentially results in a mismatch between development mode and
production mode, which can be quite problematic.

Additionally, a `package-lock.json` will not be generated unless there is a
`package.json` present in the same directory. So if Turbopack is detecting a
`package-lock.json` file outside the root of the Next.js application, such as in
the home directory (as in the case here), that indicates that there is also a
straggling `package.json` file present. When you remove the `package-lock.json`,
search for the `package.json` and remove it.

## Why paying close attention to output returned to Terminal during development is so important and how to make the process easier

Paying close attention to terminal output during software development is very
important because it serves as a critical developer tool to ensure your code
functions correctly and efficiently.

Terminal output provides immediate feedback on code execution, allowing you to
verify if specific parts of your code are working as expected. This quick
feedback speeds up the development cycle, enabling you to make adjustments and
address issues promptly.

Terminal output is used to trace how and where code is executed, which helps to
identify errors and inspect variable values at different points in the
application. This hands-on approach is vital during development, allowing you to
catch and fix issues before they become more problematic.

But there is one little problem regarding analyzing terminal output. Chances are
that the output will be very lengthy and that you can't view it all in the
console. And even if you could, it would be difficult to follow there.

No problem. The following command runs Next.js in development mode AND saves
terminal output to a file inside the root of your application directory:

```shell
# make sure that the command is executed at the root of the Next.js application
npm run dev 2>&1 | cat > output.txt
```

`npm run dev` is the script in `package.json` with the value of `next dev`. It
runs the Next.js application in the browser in development mode. It starts the
development server, permitting real-time code changes and instant feedback.

`2>&1` redirects standard error (stderr) to standard output (stdout), ensuring
both `stdout` and `stderr` output is captured.

`cat > output.txt` writes the piped output into a file named `output.txt`.

`|` is the pipe operator which is used to pass the output of one command
directly into the input of another command. Here, it passes the
`npm run dev 2>&1` command output into the input of the `cat > output.txt`. The
`cat` command simply displays the contents of `output.txt`.

## Key takeaways

If you ever encounter the Turbopack "multiple lockfile" warning in Terminal
resulting from running the `npm run dev` command, make sure to find the culprit
package-lock.json file and remove it. Turbopack's selection of this accidental
`package-lock.json` file can lead to mismatches between development mode and
production mode, which in turn can potentially break the application build.

One way to avoid such an issue is to run the `pwd` command before running
`npm install` to make sure you are at the root directory of your application.

Finally, the one habit to pick up when running your Next.js application in
development mode is to run the `npm run dev 2>&1 | cat > output.txt` command.
This enables you to save both standard output (stdout) and standard error
(stderr) to an `output.txt` file and not the Terminal console. This allows you
to read and analyze the file content and resolve any visible errors more
speedily and efficiently.

## Related Resources

- [Turbopack in Next.js: Faster Dev Builds, Common Errors, and Real Fixes](https://prateeksha.com/blog/turbopack-nextjs-faster-dev-builds-common-errors-fixes):
  _by Sumeet Shroff, prateeksha.com_
- [Turbopack](https://nextjs.org/docs/app/api-reference/turbopack): _Nextjs
  documentation_
- [Turbopack adoption guide: Overview, examples, and alternatives](https://blog.logrocket.com/turbopack-adoption-guide/):
  _by Abhinav Anshul, LogRocket_
