Angular supports many styles of markup. Other valid forms of that snippet are: Using xml namespace: <input type="checkbox" ng:model="todo.done"> Using unders

Angular supports many styles of markup. Other valid forms of that snippet are: Using xml namespace: <input type="checkbox" ng:model="todo.done"> Using underscore in the attribute name: <input type="checkbox" ng_model="todo.done"> As an x-* attribute: <input type="checkbox" x-ng-model="todo.done"> As a HTML5 data attribute: <input type="checkbox" data-ng-model="todo.done"> I think their may be a few more, but in any case, Angular is flexible enough that you can choose the representation that is best for you and your team.