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Angular sets these CSS classes. It is up to your application to provide useful styling.

## CSS classes used by angular

- `ng-invalid`, `ng-valid`

  - Usage: angular applies this class to an input widget element if that element's input does not pass validation. (see `input` directive).

- `ng-pristine`, `ng-dirty`

  - Usage: angular `input` directive applies `ng-pristine` class to a new input widget element which did not have user interaction. Once the user interacts with the input widget the class is changed to `ng-dirty`.

### Related Topics

- Angular Templates
- Angular Forms