---
source: https://iinventedlight.com/library/notes/angular-pipes.md
title: "Angular pipes transform values declaratively in a template"
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 pipes"
tags: [angular, pipes, templates, async]
client: Librarian
sources:
  - id: S1
    title: "Pipes in templates"
    publisher: Angular docs
    url: https://angular.dev/guide/templates/pipes
    accessed: 2026-11-11
    license: "CC BY 4.0"
  - id: S2
    title: "AsyncPipe"
    publisher: Angular source
    url: https://github.com/angular/angular/blob/main/packages/common/src/pipes/async_pipe.ts
    accessed: 2026-11-11
    license: "MIT"
---
# Pipes transform data in Angular template expressions

**Answer:** Pipes are special operators in Angular template expressions. They let you transform data declaratively in the template. You declare a transformation function once and then reuse it across templates. Angular pipes use the vertical bar character `|`, in the spirit of a Unix pipe.

Angular template expressions do not support bitwise operators, even though standard JavaScript uses `|` for bitwise OR.

## Built-in pipes

Angular includes built-in pipes in the `@angular/common` package. `AsyncPipe` reads a value from a `Promise` or an RxJS `Observable`. `CurrencyPipe` and `DatePipe` format numbers and dates according to locale rules.

## In source

AsyncPipe unwraps a value from an asynchronous primitive. After it subscribes, it returns the latest emitted value. When a new value is emitted, the pipe marks the view for update.

## See also

- [angular-templates](https://iinventedlight.com/library/notes/angular-templates/)
- [angular-control-flow](https://iinventedlight.com/library/notes/angular-control-flow/)

## Claims

- id: C1
  claim: Pipes transform data declaratively in a template.
  source: S1
  evidence: "Pipes are special operators in Angular template expressions"

- id: C2
  claim: AsyncPipe reads a value from a Promise or an Observable.
  source: S1
  evidence: "Read the value from a `Promise` or an RxJS `Observable`."

- id: C3
  claim: AsyncPipe unwraps a value from an asynchronous primitive.
  source: S2
  evidence: "Unwraps a value from an asynchronous primitive."

- id: C4
  claim: The async pipe subscribes to an Observable or Promise.
  source: S2
  evidence: "The `async` pipe subscribes to an `Observable` or `Promise`"

## Sources

- [S1] Pipes in templates. Angular docs. https://angular.dev/guide/templates/pipes . License: CC BY 4.0. Accessed 2026-11-11.

- [S2] AsyncPipe. Angular source. https://github.com/angular/angular/blob/main/packages/common/src/pipes/async_pipe.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.

---

Agents: [/agents.md](/agents.md) | [/.well-known/agent-library.json](/.well-known/agent-library.json).