Auto-fix

Run Knip as you normally would, and if the report looks good then run it again with the --fix flag to let Knip automatically apply fixes. It fixes the following issue types:

• Remove export keyword for unused exports and exported types
• Remove export default keywords for unused default exports
• Remove exports, re-exports and exported types
• Remove unused enum members
• Remove unused class members (disabled by default)
• Remove unused dependencies and devDependencies from package.json
• Remove unused files

Caution

Use a VCS (version control system) like Git to review and undo changes as necessary.

Flags

Add the --fix flag to remove unused exports and dependencies:

knip --fix

Add --allow-remove-files to allow Knip to remove unused files:

knip --fix --allow-remove-files

Use --fix-type to fix only specific issue types:

• files
• exports
• types
• dependencies

Example:

knip --fix-type exports,types
knip --fix-type exports --fix-type types   # same as above

Demo

Post-fix

After Knip has fixed issues, there are four things to consider:

1. Use a formatter

Use a tool like Prettier or Biome if the code needs formatting. Knip removes the minimum amount of code while leaving it in a working state.

2. Unused variables

Use a tool like ESLint or Biome to find and remove unused variables inside files. This may result in more deleted code, and Knip may then find more unused code. Rinse and repeat!

3. Unused dependencies

Verify changes in package.json and update dependencies using your package manager.

npm

npm install

pnpm

pnpm install

bun

bun install

yarn

yarn

4. Install unlisted dependencies

If Knip reports unlisted dependencies or binaries, they should be installed.

npm

npm install unlisted-package

pnpm

pnpm add unlisted-package

bun

bun add unlisted-package

yarn

yarn add unlisted-package

Example results

Exports

The export keyword for unused exports is removed:

module.ts

export const unused = 1;
export default class MyClass {}
const unused = 1;
class MyClass {}

The default keyword was also removed here.

Knip removes the whole or part of export declarations:

module.ts

type Snake = 'python' | 'anaconda';
const Owl = 'Hedwig';
const Hawk = 'Tony';
export type { Snake };
export { Owl, Hawk };
;
;

Re-exports

Knip removes the whole or part of re-exports:

file.js

export { Cat, Dog } from './pets';
export { Lion, Elephant } from './jungle';
export { Elephant } from './jungle'

Also across any chain of re-exports:

module.ts

export const Hawk = 'Tony';
export const Owl = 'Hedwig';
const Owl = 'Hedwig';

barrel.ts

export * from './module.js';

index.ts

export { Hawk, Owl } from './barrel.js';
export { Hawk } from './barrel.js'

Export assignments

Knip removes individual exported items in “export assignments”, but does not remove the entire export declaration if it’s empty:

file.js

export const { a, b  } = fn();
export const {   } = fn();

export const [c, d] = [c, d];
export const [, ] = [c, d];

Reason: the right-hand side of the assignment might have side-effects. It’s not safe to always remove the whole declaration. This could be improved in the future (feel free to open an issue/RFC).

Enum members

Unused members of enums are removed:

file.ts

export enum Directions {
  North = 1,
  East = 2,
  South = 3,
  West = 4,
}

CommonJS

Knip supports CommonJS and removes unused exports:

common.js

module.exports = { identifier, unused };
module.exports = { identifier,  };

module.exports.UNUSED = 1;
module.exports['ACCESS'] = 1;

Warning: the right-hand side of such an assignment might have side-effects. Knip currently removes the whole declaration (feel free to open an issue/RFC).

Dependencies

Unused dependencies are removed from package.json:

package.json

{
  "name": "my-package",
  "dependencies": {
    "rimraf": "*",
    "unused-dependency": "*"
    "rimraf": "*"
  },
  "devDependencies": {
    "unreferenced-package": "5.3.3"
  }
  "devDependencies": {}
}

Class members   experimental

Unused members of classes can be removed:

file.ts

export class Rectangle {
  constructor(public width: number, public height: number) {}

  static Key = 1;


  area() {
    return this.width * this.height;
  }

  public get unusedGetter(): string {
    return 'unusedGetter';
  }
}

Currently Knip might be too eager removing class members when they’re not referenced internally but meant to be called by an external library. For instance, Knip might think componentDidMount and render in React class component are unused and will remove those.

Note that classMembers aren’t included by default.

What’s not included

Operations that auto-fix does not (yet) perform and why:

• Add unlisted (dev) dependencies to package.json (should it go into dependencies or devDependencies? For monorepos in current workspace or root?)
• Add unlisted binaries (which package and package version contains the used binary?)
• Fix duplicate exports (which one should removed?)