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Answer: When you use a component, you commonly want to pass data into it. The child declares the data it accepts as inputs. You then bind to that property in a template. If you're familiar with other web frameworks, input properties are similar to props.

The input function

The input function has special meaning to the Angular compiler. You can call it only in component and directive property initializers. It returns an InputSignal. You read the value by calling the signal. Signals created by input are read-only.

Input declarations are recorded statically at compile-time. Inputs cannot be added or removed at run-time. Input names are case-sensitive. When you extend a component class, the child class inherits the inputs.

If an input has no default and is not set, its value is undefined. Call input.required instead of input to declare a required input. Angular reports an error at build time if a required input is missing in a template.

In source

The input function is how you declare inputs in directives and components. It also exposes input.required for required inputs.

See also

• angular-outputs
• angular-components

Claims

• id: C1 claim: A component declares the data it accepts as inputs. source: S1 evidence: "A component specifies the data that it accepts by declaring"

• id: C2 claim: The input function returns a read-only InputSignal. source: S1 evidence: "The input function returns an InputSignal."

• id: C3 claim: Call input.required to declare a required input. source: S1 evidence: "You can declare that an input is required by calling input.required instead of input:"

• id: C4 claim: input declares inputs on directives and components. source: S2 evidence: "The input function allows declaration of inputs in directives and"

Sources

• [S1] Component inputs. Angular docs. https://angular.dev/guide/components/inputs . License: CC BY 4.0. Accessed 2026-11-11.

• [S2] input() function. Angular source. https://github.com/angular/angular/blob/main/packages/core/src/authoring/input/input.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_d0q0nxag,
  author = {{iinventedlight}},
  title = {{Angular component inputs accept data from a parent template}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-11},
  url = {https://iinventedlight.com/library/notes/angular-inputs/},
  note = {Permanent ID iil:note:d0q0nxag. License: CC-BY-4.0.},
}

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