---
source: https://iinventedlight.com/library/notes/angular-dependency-injection.md
title: "Angular dependency injection supplies classes with their dependencies"
license: CC-BY-4.0
license_url: https://creativecommons.org/licenses/by/4.0/
source_license: "CC BY 4.0 (Angular docs, footer-verified); MIT (angular/angular source); prose restates cited source lines in own words"
license_family: angular-docs-ccby
attribution: "Summary by iinventedlight (AI-assisted). Sources: Angular docs, CC BY 4.0 text (angular/angular adev footer); Angular source, MIT (angular/angular). Notices: Angular documentation (angular/angular adev): Copyright (c) 2010-2026 Google LLC; CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Angular source (angular/angular): Copyright (c) 2010-2026 Google LLC; MIT (https://raw.githubusercontent.com/angular/angular/main/LICENSE)."
author: "iinventedlight (synthesis of cited sources); text drafted with AI assistance"
date: 2026-11-11
status: published
approved_by: "Cole Withington, 2026-11-11 09:59 PT, Librarian chat widget t34s5: \"Yes, publish all 25 Angular and Vite drafts\""
checked_on: 2026-11-11
as_of: 2026-11-11
confidence: medium
untested: "No project was run for this note; only the fetched documentation and source files were read."
category: coding-references
topic_area: "code-web: Angular dependency injection"
tags: [angular, dependency-injection, injector, providers]
client: Librarian
sources:
  - id: S1
    title: "Dependency injection in Angular"
    publisher: Angular docs
    url: https://angular.dev/guide/di
    accessed: 2026-11-11
    license: "CC BY 4.0"
  - id: S2
    title: "Injector"
    publisher: Angular source
    url: https://github.com/angular/angular/blob/main/packages/core/src/di/injector.ts
    accessed: 2026-11-11
    license: "MIT"
---
# Angular dependency injection supplies a class with the objects it needs

**Answer:** Dependency injection is a design pattern used to organize and share code across an application. You supply dependencies to a class instead of creating them inside it. A dependency is any object, value, function, or service that a class needs but does not create itself.

## Why Angular uses it

DI helps you reuse functionality as an application grows. It supports a clearer separation of concerns, makes code easier to refactor, and lets unit tests substitute test doubles for real implementations.

You interact with the system in two main ways: you provide a dependency, or you inject a provided dependency into a class that needs it.

## Injectors

Concrete injectors implement the `Injector` interface. They are configured with providers that associate dependency types with injection tokens. `Injector.get` retrieves an instance from the injector based on a provided token.

## See also

- [angular-http-client](https://iinventedlight.com/library/notes/angular-http-client/)
- [angular-directives](https://iinventedlight.com/library/notes/angular-directives/)

## Claims

- id: C1
  claim: DI supplies dependencies to a class instead of creating them inside it.
  source: S1
  evidence: "by supplying dependencies to a class instead of creating them inside it."

- id: C2
  claim: A dependency is something a class needs but does not create itself.
  source: S1
  evidence: "A dependency is any object, value, function, or service"

- id: C3
  claim: Concrete injectors implement the Injector interface.
  source: S2
  evidence: "Concrete injectors implement this interface."

- id: C4
  claim: get retrieves an instance from the injector by token.
  source: S2
  evidence: "Retrieves an instance from the injector based on the provided token."

## Sources

- [S1] Dependency injection in Angular. Angular docs. https://angular.dev/guide/di . License: CC BY 4.0. Accessed 2026-11-11.

- [S2] Injector. Angular source. https://github.com/angular/angular/blob/main/packages/core/src/di/injector.ts . License: MIT. Accessed 2026-11-11.


License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted). Sources and notices: Angular documentation (angular/angular adev): Copyright (c) 2010-2026 Google LLC; CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Angular source (angular/angular): Copyright (c) 2010-2026 Google LLC; MIT (https://raw.githubusercontent.com/angular/angular/main/LICENSE). Text was condensed and changed from the originals.

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