HTML: Checkbox default value

Question

When I submit a HTML form with a checked checkbox that doesn\'t have an explicitly defined value, Chrome sends on as a value for that field.

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Answer 1

The HTML 4.01 specification does not specify the value of a checked checkbox. It just refers it saying that it is “on”, but this is just prose and does not say what the default value is. But it also says (under the description of the input element) that the value attribute is required in this case.

So has undefined behavior as regards to the value used, though in practice browsers use value=on as the default.