A switch device is an input for people with severely limited movement, and the picture most people have is a single large button pressed with a hand, head or knee. That picture is now only half of it. On a current phone a switch can be a mouth sound, a head turn the front camera picks up, or a pinch of finger and thumb. It can be a double tap on the back of the case. None of those needs extra hardware. Software then steps through the interactive elements on screen and the user fires the switch when the highlight reaches the one they want. On the web that stepping runs on whatever the keyboard interface can reach, which is why keyboard support is the work that serves these readers. Anything mouse-only drops out of the scan and is left to a slower fallback that aims a pointer by hand.
In practice
A switch is whatever movement a person has. A button pressed with a hand, head or foot, a tube operated by sipping and puffing, a joystick, an adaptive controller, or one key on an ordinary keyboard assigned to the job. Be careful with the words, though. Apple and Google do not share a vocabulary for any of this, so the scanning styles named in one platform's documentation are not the ones named in the other's.
Scanning is the interaction model and it is where the cost lives. The interface highlights each item in turn and the user fires the switch when it reaches the one they want, so reaching the twentieth thing in a linear scan costs twenty steps. Scanning by row and then by item inside the row cuts that down, and either way every extra focusable element on the page is seconds somebody pays, every time. Landing on the item is usually not the end of it either, because a menu of available actions then opens, and choosing from that is a second round of scanning.
When scanning cannot reach something, the fallback is point scanning, and it is slow. A vertical line glides across the screen and the user stops it. Then a horizontal line glides down and they stop that. The pointer lands where the two cross, sometimes after a second, finer pass. That is what a switch user is left with when the keyboard interface fails, and it is why target size matters here as much as it does on a touchscreen.
We looked for a figure on how many people use switches and did not find a usable one. The nearest thing our search turned up is thirteen years old, had 46 respondents, and rests its switch figure on a single person. If somebody needs a number, the honest answer is that we have not found one worth quoting, and repeating that survey would be worse than saying so.
Why it matters
Inside your page, switch access runs on what the keyboard interface exposes. If Tab cannot reach it, the scan does not reach it either. A keyboard trap does not merely slow a switch user down, it costs them the page, because the way out is no longer inside your content. Switch software offers system actions of its own, so Home and Back are usually still there and your site is what they have to leave. The scanner has a step-out for a group it has moved inside. A page that traps focus offers nothing of the kind. It is also why the timing rule's numbers are what they are. Twenty seconds to hit any switch is what the standard treats as enough for almost everybody, including people with reduced movement, and the rest of that criterion is built out from there.
What every extra stop costs
Add a decorative element to the tab order and a mouse user never notices. A switch user scanning linearly waits for it on every pass, on every page, before reaching anything they came for. That is the argument for a lean focus order, and it is the same argument bypass blocks was written to solve.
Where this shows up on the site
Related terms
- Keyboard accessibilityKeyboard accessibility means every piece of functionality on the page can be operated through a keyboard interface.
- Focus orderFocus order is the sequence focus travels in as you press Tab, and by default it follows the order elements appear in the code rather than the order they appear on screen.
- Motor disabilityMotor disability covers anything that affects movement, strength, precision or sensation, from tremor and arthritis to multiple sclerosis, repetitive strain, paralysis and missing limbs.
- Assistive technologyAssistive technology is hardware or software that gives a person with a disability more than a mainstream browser offers on its own.
- Target sizeTarget size is how big a clickable or tappable thing is, and two WCAG rules govern it at two different numbers.
Knowing the word is the easy part.
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