An element that can be turned on and off. This is most commonly rendered as a box when the element is off and a box with a check when the element is on. The user can switch the state of the check box by selecting it with the mouse. A label, specified with the label attribute, may be added beside the check box.
More information is available in the XUL tutorial.

<checkbox label="Enable JavaScript" checked="true"/> <checkbox label="Enable Java" checked="false"/>
accesskeylabel attribute for the element.
checkedhasAttribute() to determine whether this attribute is set instead of getAttribute().type attribute must be set to checkbox or radio for this attribute to have any effect.cropcrop attribute. An ellipsis will be used in place of the cropped text. If the box direction is reversed, the cropping is reversed.startendleftrightcenternonenone and the displayed text is larger than this maximum width, you may be able to use the max-width CSS property (or the maxwidth attribute) to override this size. For example, for a menuitem in a menu you can add the following CSS rule when you want to use the value none:menupopup > menuitem, menupopup > menu { max-width: none; }
disabledcommand event will not fire. In the case of form elements, it will not be submitted. Do not set the attribute to true, as this will suggest you can set it to false to enable the element again, which is not the case.
disabled attribute is allowed only for form controls. Using it with an anchor tag (an <a> link) will have no effect.disabled property which, except for menus and menuitems, is normally preferred to use of the attribute, as it may need to update additional state.srcpreferencepreference. This attribute only has any effect when used inside a prefwindow. More information is available in the Preferences System article.tabindextab" key. Elements with a higher tabindex are later in the tab sequence.accessibleTypensIAccessibleProvider, nsIDOMXULCheckboxElement