The "Checkbox Hack" is where you use a connected
<input type="checkbox"> and usually some other element you are trying to control, like this:
<label for="toggle">Do Something</label> <input type="checkbox" id="toggle"> <div class="control-me">Control me</div>
Then with CSS, you hide the checkbox entirely. Probably by kicking it off the page with absolute positioning or setting its opacity to zero. But just because the checkbox is hidden, clicking the
<label> still toggles its value on and off. Then you can use the adjacent sibling combinator to style the
<div> differently based on the
:checked state of the input.
So you can style an element completely differently depending on the state of that checkbox, which you don't even see. Pretty neat. Let's look at a bunch of things the "Checkbox Hack" can do.
Custom Designed Radio Buttons and Checkboxes
You can hide the default UI of a radio button or checkbox, and display a custom version right on top of it.
File system like "tree menu"
The "tabs" design pattern is just toggling on and off of areas, perfect for the checkbox hack. But instead of checkboxes, in which any checkbox can be on or off independently of one another, these tabs use radio buttons in which only one per group can be on at a time (like how only one tab can be active at a time).
Demo from Functional CSS tabs revisited:
A toggle can take the form of ON/OFF, which can be done with a single
<input type="checkbox">. Like emoji toggles!
Or it could be multiple
<input type="checkbox"> elements to switch between differnet distinct values.
FAQ Answer Revealing
You'd probably just use a
<summary> combo for this these days, but expandable sections can be done with the checkbox hack.
Hide the Sidebar
Like the old school Octopress theme.