html - What values for checked and selected are false?

Question

I think according to W3 spec, you're supposed to do

<input type="checkbox" checked="checked" />

And

 selected="selected"

But, most browsers will accept it you just write "CHECKED" and don't give it a value. So, what if you do include the attribute, are there any values that would be (consistently) considered false?

Answer 1

There are no values that will cause the checkbox to be unchecked. If the checked attribute exists, the checkbox will be checked regardless of what value you set it to.

<input type="checkbox" checked />
<input type="checkbox" checked="" />
<input type="checkbox" checked="checked" />
<input type="checkbox" checked="unchecked" />
<input type="checkbox" checked="true" />
<input type="checkbox" checked="false" />
<input type="checkbox" checked="on" />
<input type="checkbox" checked="off" />
<input type="checkbox" checked="1" />
<input type="checkbox" checked="0" />
<input type="checkbox" checked="yes" />
<input type="checkbox" checked="no" />
<input type="checkbox" checked="y" />
<input type="checkbox" checked="n" />