no-skip-lib-check

Discourage skipLibCheck: true because it silences type errors in declaration files from dependencies, masking real bugs.

Targeted pattern scope

The compilerOptions.skipLibCheck field in any tsconfig*.json file.

What this rule reports

This rule reports when compilerOptions.skipLibCheck is set to true.

Why this rule exists

skipLibCheck: true tells TypeScript to skip type-checking of all .d.ts files. While this can speed up compilation and unblock projects with broken third-party type definitions, it has a high cost: any type error in a dependency's declaration file — including errors that would affect your own code — is silently ignored.

Common consequences include:

A dependency ships a broken overload. Without skipLibCheck TypeScript would report it at the call site; with skipLibCheck the call compiles but fails at runtime.
A package's .d.ts uses a type that conflicts with a sibling dependency. skipLibCheck hides the conflict, leaving it to surface as a runtime exception.

The recommended alternative is to update the dependency, override the type with a local declaration, or use skipDefaultLibCheck to skip only the TypeScript built-in libraries if that is the specific pain point.

❌ Incorrect

{
    "compilerOptions": {
        "skipLibCheck": true
    }
}

✅ Correct

Remove the option entirely or set it to false:

{
    "compilerOptions": {
        "strict": true
    }
}

If only the built-in TypeScript lib files are causing issues:

{
    "compilerOptions": {
        "skipDefaultLibCheck": true
    }
}

When not to use it

Disable this rule when a third-party dependency ships incompatible declaration files that cannot be patched or overridden, and the only way to unblock the project in the short term is skipLibCheck: true. Track the root cause as a separate issue.

Package documentation

Rule catalog ID: R013

Targeted pattern scope​

What this rule reports​

Why this rule exists​

❌ Incorrect​

✅ Correct​

When not to use it​

Package documentation​

Further reading​