How to fix npm ERR! code EUNKNOWNWORKSPACE npm ERR! Unknown workspace: "package-name" in npm

Open your project's root package.json and check the 'workspaces' field to confirm it includes the directory pattern containing your workspace.

{
  "name": "my-monorepo",
  "workspaces": [
    "packages/*"
  ]
}

Make sure the glob pattern matches your actual folder structure.

Open the package.json file inside the workspace directory and verify the 'name' field. This is the identifier npm uses.

{
  "name": "@myapp/frontend",
  "version": "1.0.0"
}

If the workspace folder is 'packages/frontend', but the name is '@myapp/frontend', you must use '@myapp/frontend' when referencing it in npm commands.

Replace your command with the correct workspace package name. Use the 'name' field from the workspace's package.json, not the folder name.

# Incorrect - uses folder name
npm run build -w frontend

# Correct - uses package name from package.json
npm run build -w @myapp/frontend

You can also run commands in all workspaces by omitting the -w flag entirely: npm run build

Run npm with the --workspaces flag to see all configured workspaces and their actual package names:

npm run --workspaces

# Or use npm list to see all workspaces:
npm list --workspaces

This will show you the exact package names npm recognizes for your workspaces.

If you've recently changed workspace configuration or package names, clear npm's cache and reinstall dependencies:

npm cache clean --force
rm package-lock.json
npm install

This ensures npm's internal workspace registry is updated with the correct workspace names.