# Override Clerk interfaces with custom types

Clerk provides TypeScript interfaces that you can use to define custom types for your application. Custom types provide auto-complete and prevent TypeScript errors. You can define custom types for the following:

- `ClerkAuthorization`
- `CustomJwtSessionClaims`
- `OrganizationPublicMetadata`
- `OrganizationInvitationPublicMetadata`
- `OrganizationMembershipPublicMetadata`
- `SignUpUnsafeMetadata`
- `UserPublicMetadata`
- `UserPrivateMetadata`
- `UserUnsafeMetadata`

## Example: custom JWT claims

To override an interface, you must define a global type, as shown in the following example:

1. In your application's root folder, add a `types` directory.
2. Inside of the `types` directory, add a `globals.d.ts` file.
3. Create the `CustomJwtSessionClaims` interface and declare it globally.
4. Add the custom claims to the `CustomJwtSessionClaims` interface.

filename: types/globals.d.ts
```ts
export {}

declare global {
  interface CustomJwtSessionClaims {
    firstName?: string
    primaryEmail?: string
    metadata: {
      onboardingComplete?: boolean
    }
  }
}
```

## Example: custom Roles and Permissions

When defining custom types for Roles and Permissions:

- Custom Permissions are merged with [System Permissions](https://clerk.com/docs/guides/organizations/control-access/roles-and-permissions.md#system-permissions)
- Custom Roles completely replace default Roles (`org:admin` and `org:member`)

filename: types/globals.d.ts
```tsx
export {}

declare global {
  interface ClerkAuthorization {
    permission: 'org:quiz:create' | 'org:quiz:grade' | 'org:quiz:read' | 'org:quiz:fill'
    role: 'org:super_admin' | 'org:teacher' | 'org:student'
  }
}
```

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