No unused dependencies in package.json

Unused production dependencies add bundle weight, extend install time, and expand your attack surface — every extra package is a potential supply chain compromise vector. CWE-1357 (Reliance on Insufficiently Trustworthy Component) applies: dependencies you didn't intend to ship still ship. AI-generated codebases accumulate unused packages frequently: the model installs axios and moment in one session, then the next session uses native fetch and inline date formatting without removing the earlier additions.

Run a dependency check to find unused packages:

npx depcheck

Verify each reported unused package before removing — some packages are loaded via config rather than imports (ESLint plugins, Babel presets). For confirmed unused packages:

npm uninstall axios moment lodash

Also audit whether production dependencies have been misplaced as devDependencies or vice versa. For deeper supply chain analysis, the Dependency & Supply Chain Audit covers version pinning, lockfile integrity, and provenance checks.

• ID: no-unused-deps

• Severity: medium

• What to look for: Compare the packages listed in package.json dependencies and devDependencies against actual usage in source files. Look for packages that:

  • Appear in dependencies but are never imported in any source file
  • Were added during AI-assisted development but whose functionality ended up unused
  • Duplicate functionality of another installed package

  Focus especially on dependencies (production) vs. devDependencies (development-only) — packages used only in tests or build scripts should be in devDependencies, not dependencies. Tools like depcheck can automate this analysis; check if it's in the project's scripts.

• Pass criteria: Count every package in dependencies and check each for at least one import in source code. No more than 2 packages in dependencies appear to be unused (not imported anywhere in source code). Report the count even on pass: "X of Y production dependencies are actively imported."

• Fail criteria: 3 or more packages in dependencies are never imported in source code, OR multiple packages in devDependencies appear to be production dependencies misplaced there (or vice versa).

• Skip (N/A) when: The project has fewer than 5 total dependencies. Signal: dependencies + devDependencies combined has fewer than 5 entries.

• Detail on fail: "3 unused packages found in dependencies: 'axios' (never imported — project uses native fetch), 'moment' (never imported — date formatting done inline), 'lodash' (never imported). These add ~150KB to the bundle unnecessarily." or "5 packages in dependencies should be in devDependencies: jest, @types/jest, ts-jest, @testing-library/react, @testing-library/jest-dom."

• Remediation: Unused dependencies bloat your install time, bundle size, and attack surface. Run a dependency check:

  npx depcheck
  

  For each unused package reported, verify it's truly unused (some packages are loaded via config, not imports — e.g., ESLint plugins) before removing. To remove:

  npm uninstall axios moment lodash
  

  For a deeper analysis of dependency risks and supply chain health, the Dependency & Supply Chain Audit covers this in detail.