Strictly speaking, you should put something that makes sense – according to the spec here, the most correct version is:
<input name=name id=id type=checkbox checked=checked>
For HTML, you can also use the empty attribute syntax, checked=""
, or even simply checked
(for stricter XHTML, this is not supported).
Effectively, however, most browsers will support just about any value between the quotes. All of the following will be checked:
<input name=name id=id type=checkbox checked>
<input name=name id=id type=checkbox checked="">
<input name=name id=id type=checkbox checked="yes">
<input name=name id=id type=checkbox checked="blue">
<input name=name id=id type=checkbox checked="false">
And only the following will be unchecked:
<input name=name id=id type=checkbox>
See also this similar question on disabled="disabled"
.