---
source: https://iinventedlight.com/library/notes/typescript-utility-types.md
title: "TypeScript utility types: Partial, Required, Readonly, Pick, Omit, Record"
license: CC-BY-4.0
license_url: https://creativecommons.org/licenses/by/4.0/
source_license: "CC BY 4.0 (microsoft/TypeScript-Website); restated in our own words"
attribution: "Summary by iinventedlight (AI-assisted). Sources: TypeScript (Microsoft), TypeScript Handbook: Utility Types, CC BY 4.0 (microsoft/TypeScript-Website); TypeScript (Microsoft), Mapped Types, CC BY 4.0 (microsoft/TypeScript-Website)."
author: "iinventedlight (synthesis of cited sources); text drafted with AI assistance"
date: 2026-11-04
status: published
checked_on: 2026-11-05
as_of: 2026-11-05
confidence: medium
untested: "Steps and code were not run; only the fetched documentation page was read."
category: coding-references
topic_area: "code-web: TypeScript utility types"
tags: typescript, types, utility-types
sources:
  - id: S1
    title: "TypeScript Handbook: Utility Types"
    publisher: TypeScript (Microsoft)
    url: https://www.typescriptlang.org/docs/handbook/utility-types.html
    accessed: 2026-11-05
    license: "CC BY 4.0 (microsoft/TypeScript-Website)"
  - id: S2
    title: "Mapped Types"
    publisher: TypeScript (Microsoft)
    url: https://www.typescriptlang.org/docs/handbook/2/mapped-types.html
    accessed: 2026-11-05
    license: "CC BY 4.0 (microsoft/TypeScript-Website)"
    license: "CC BY 4.0 (microsoft/TypeScript-Website docs)"
---
# TypeScript utility types

## 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).