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Why Bitwarden Is Moving Away from TypeScript enums

Following an architecture discussion we've decided to stop using TypeScript enums in favor of a safer and more maintainable alternative.

Reasons include:​

  • ✅ Type-safe
  • ✅ Smaller bundle size
  • ✅ Flexible and extendable
  • ✅ Fewer surprises

Instead of using enums, we use constant objects and derive union types:

Safe Alternative:

export const CipherTypes = {
  Login: 1,
  SecureNote: 2,
  Card: 3,
  Identity: 4,
  SshKey: 5,
} as const;

export type CipherTypeValue = (typeof CipherTypes)[keyof typeof CipherTypes];

declare function useCipher(type: CipherTypeValue): void;

useCipher(CipherTypes.Login); // ✅ Valid
useCipher(42); // ❌ Invalid

The Problems with enums​

1. enums Emit Extra Code​

TypeScript enums generate additional JavaScript code at compile time, increasing bundle size and potentially degrading performance.

Example:

export enum CipherType {
  Login = 1,
  SecureNote = 2,
  Card = 3,
  Identity = 4,
  SshKey = 5,
}

Compiled Output:

var CipherType;
(function (CipherType) {
  CipherType[(CipherType["Login"] = 1)] = "Login";
  CipherType[(CipherType["SecureNote"] = 2)] = "SecureNote";
  CipherType[(CipherType["Card"] = 3)] = "Card";
  CipherType[(CipherType["Identity"] = 4)] = "Identity";
  CipherType[(CipherType["SshKey"] = 5)] = "SshKey";
})(CipherType || (CipherType = {}));

2. Numeric enums Are Not Type Safe​

TypeScript allows arbitrary numbers to be passed to functions expecting a numeric enum.

Example:

declare function useCipher(type: CipherType): void;

useCipher(42); // This compiles! 😱

This undermines the purpose of type safety and can introduce hard-to-track bugs.

3. enums Are Named Types​

Even when using string or numeric enums, their named type behavior reduces compatibility with structurally similar values.

Resources Used​

https://dev.to/ivanzm123/dont-use-enums-in-typescript-they-are-very-dangerous-57bh https://www.typescriptlang.org/docs/handbook/enums.html#objects-vs-enums https://devblogs.microsoft.com/typescript/announcing-typescript-5-8-beta/#the---erasablesyntaxonly-optio