What are Pick and Omit utility types and when should you use them?

Pick<T, K> — creates a type with only the specified keys from T:

interface User {
  id: number;
  name: string;
  email: string;
  password: string;
  createdAt: Date;
}

// Only expose safe fields to the client
type PublicUser = Pick<User, 'id' | 'name' | 'email'>;
// { id: number; name: string; email: string }

// Safe to serialize and send over the wire
function getUserPublic(id: number): PublicUser {
  const user = findUser(id);
  return { id: user.id, name: user.name, email: user.email };
}

Omit<T, K> — creates a type with the specified keys removed:

// Remove sensitive fields
type SafeUser = Omit<User, 'password'>;

// Remove auto-managed fields for create inputs
type CreateUserInput = Omit<User, 'id' | 'createdAt'>;
// { name: string; email: string; password: string }

function createUser(input: CreateUserInput): User {
  return { ...input, id: generateId(), createdAt: new Date() };
}

Pick vs Omit — when to choose:

• Use Pick when you want a small subset from a large type — clearly states which fields you want
• Use Omit when you want most fields minus a few — less fragile when new fields are added (they're included automatically)