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Short answer

Utility types are built-in helpers such as Partial, Required, Record, and NonNullable. Many of them are thin wrappers over mapped types. [S1][S2]

Points

• Partial<Type> makes every property optional. [S1]
• Record<Keys, Type> builds an object type from keys and a value type. [S1]
• Required<Type> makes every property required (the opposite of Partial). [S1]
• Mapped types can add readonly or ? while mapping keys. [S2]

Claims

• id: C1 claim: Partial makes all properties optional. source: S1 evidence: "Constructs a type with all properties of Type set to optional"
• id: C2 claim: Record builds an object type from keys and a type. source: S1 evidence: "Constructs an object type whose property keys are Keys"
• id: C3 claim: Required constructs a type with all properties required. source: S1 evidence: "Constructs a type consisting of all properties of Type set to required"
• id: C4 claim: Mapped types can apply readonly and optional modifiers. source: S2 evidence: "two additional modifiers which can be applied during mapping: readonly and ?"

Sources

• [S1] TypeScript Handbook: Utility Types. TypeScript (Microsoft). https://www.typescriptlang.org/docs/handbook/utility-types.html . License: CC BY 4.0 (microsoft/TypeScript-Website). Accessed 2026-11-05.
• [S2] Mapped Types. TypeScript (Microsoft). https://www.typescriptlang.org/docs/handbook/2/mapped-types.html . License: CC BY 4.0 (microsoft/TypeScript-Website). Accessed 2026-11-05.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

Source notice: TypeScript Handbook / Website docs © Microsoft. Licensed under Creative Commons Attribution 4.0 International (https://github.com/microsoft/TypeScript-Website/blob/v2/LICENSE).

@misc{iil_note_jcgkj2xj,
  author = {{iinventedlight}},
  title = {{TypeScript utility types: Partial, Required, Readonly, Pick, Omit, Record}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/typescript-utility-types/},
  note = {Permanent ID iil:note:jcgkj2xj. License: CC-BY-4.0.},
}

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