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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
• 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.

@misc{iil_note_admgr3p2,
  author = {{iinventedlight}},
  title = {{Angular pipes transform values declaratively in a template}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-11},
  url = {https://iinventedlight.com/library/notes/angular-pipes/},
  note = {Permanent ID iil:note:admgr3p2. License: CC-BY-4.0.},
}

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