How to fix npm WARN publish npm WARN publish No license field in npm

npmBEGINNERMEDIUMUpdated Dec 5, 2025· 142 views

This warning appears when your package.json file lacks a license field. npm displays this to indicate that your package metadata is incomplete and users won't know what rights they have to use, modify, or distribute your code.

Quick fix

Fixes npm WARN publish npm WARN publish No license field

{
  "name": "my-package",
  "version": "1.0.0",
  "license": "MIT"
}
  1. Choose an appropriate license
  2. Add the license field to package.json
  3. Create a LICENSE file
  4. Verify the license field is valid
npm — error
{
  "name": "my-package",
  "version": "1.0.0",
  "license": "MIT"
}
npm WARN publish npm WARN publish No license field

What this error means

This warning appears when your package.json file lacks a license field. npm displays this to indicate that your package metadata is incomplete and should not be published without proper license information. The warning means: "This package lacks proper licensing information—if you try to publish it, users won't know what rights they have to use, modify, or distribute your code." Without a license field, it's legally unclear who can use your code and how. Users downloading your package have no explicit rights to modify, distribute, or use it commercially—even if you intended to allow it.

Typical symptoms

  • npm WARN package.json [package-name] No license field appears during install or publish
  • Third-party license scanning tools report the package as unlicensed
  • Users cannot legally determine usage rights
  • CI/CD pipelines flag the package as non-compliant

Common causes

  1. License field was never added to package.json during project setup
  2. License field was accidentally removed from package.json
  3. License value is invalid or not SPDX-compliant format
  4. Developer assumed license was optional for private packages

How to fix "npm WARN publish npm WARN publish No license field"

1Choose an appropriate license

Select a license based on your project type:

Permissive licenses (best for broad adoption):
- MIT: Most popular for npm packages. Simple, allows commercial use.
- Apache-2.0: Includes patent protection.
- ISC: Functionally identical to MIT, npm's default.

Copyleft licenses (require derivative works to be open source):
- GPL-3.0-or-later: Strong copyleft with patent protection.

For proprietary/private projects:
- UNLICENSED: Explicitly grants no rights.

View the complete SPDX License List at https://spdx.org/licenses/

2Add the license field to package.json

Open your package.json and add the license field with a valid SPDX identifier:

json
{
  "name": "my-package",
  "version": "1.0.0",
  "license": "MIT"
}

For proprietary/unlicensed code:

json
{
  "license": "UNLICENSED",
  "private": true
}
3Create a LICENSE file

Create a LICENSE file (no extension) in your project root directory.

1. Download the full license text from choosealicense.com or spdx.org/licenses/
2. Save as LICENSE in your project root
3. Update copyright year and author name if required

Example structure:

bash
project/
├── LICENSE
├── package.json
├── src/
└── README.md
4Verify the license field is valid

Validate that your license field uses proper SPDX format:

bash
npm view . license

Common mistakes to avoid:
- "MIT License" instead of "MIT" (use short form only)
- "Apache 2.0" instead of "Apache-2.0" (missing hyphen)
- "GPLv3" instead of "GPL-3.0-or-later" (use proper SPDX)
- "UNLICENSE" instead of "UNLICENSED" (different meaning)

Advanced notes

SPDX Standard: The Software Package Data Exchange (SPDX) standard is adopted by npm, Python, Rust Cargo, and other major package managers. Using SPDX identifiers ensures your license is machine-readable and globally recognized.

License Expressions: npm supports compound license expressions:
- (MIT OR Apache-2.0) - User can choose either license
- (MIT AND Apache-2.0) - Both licenses apply
- GPL-2.0-or-later WITH Bison-exception-2.2 - Base license plus exception

For Proprietary Code: Never use "All Rights Reserved" (not SPDX-compliant). Use UNLICENSED instead. Combine with "private": true to prevent accidental npm registry publication.

Legal Implications: In cases like Artifex v. Hancom, copyright/license violations led to legal action. Always specify a license to be explicit about usage rights.

Frequently asked questions

What does "npm WARN publish npm WARN publish No license field" mean?
json file lacks a license field. npm displays this to indicate that your package metadata is incomplete and should not be published without proper license information. " Without a license field, it's legally unclear who can use your code and how.
How do I fix "npm WARN publish npm WARN publish No license field"?
This warning appears when your package.json file lacks a license field. npm displays this to indicate that your package metadata is incomplete and users won't know what rights they have to use, modify, or distribute your code.
What causes "npm WARN publish npm WARN publish No license field"?
License field was never added to package.json during project setup License field was accidentally removed from package.json License value is invalid or not SPDX-compliant format
Is the "npm WARN publish npm WARN publish No license field" error serious?
It is a medium-severity error — more of a blocker than a risk. The steps above resolve it.

Official resources & further reading