Admiral Ackbar is letting us know something important. When we navigate by keyboard, we need to make certain of one thing. Make sure that a user doesn’t get trapped with no where to go.
This seems really simple, but it gets complicated quickly. And I know what seems simple to one person is traumatically difficult for another. Let’s talk about what a trap is, some examples, and ways to prevent them.
What is a keyboard trap?
A keyboard trap is any control that receives focus, but does not release it. Usually, the keyboard is trapped from moving in any direction. Sometimes it may be trapped in one direction, generally forward.
I’ve encountered some that prevent moving forward, but allow moving backward. Usually this presents a workaround, but not always. Even if there is a word around, it is still a violation.
Often developers will put a “forward” action on an input when the content meets a certain regex or pattern. This is difficult because the input is saying, “If I have 5 numbers, tab to the next control.” This becomes a keyboard trap as the keyboard only user cannot tab back into the field to correct it.
More common though is a disclosure control that isn’t following the <h3><button>Title</button><h3> pattern. Often the button is somewhere else or outside the heading. When the control is in focus, nothing happens.
How do we test?
If you do not need a screen reader to understand the screen, turn it off. If you require a screen reader, put it in forms mode. Forms mode will only respond to Tabbing and form control with the default keys. We don’t want interference from the AT.
Tab. Again. Shift tab. Keep using tab to navigate through the page, and do it in reverse. If you get stuck, try using the Escape key. Did that get you out? if yes, did it push you backwards or forwards?
If you find you can escape the trap, try repeating the situation in both directions multiple times. If you got out, this belongs in usability advice. If you can’t get out or can’t move in both directions, you have a violation.
What is the cause?
In most cases of keyboard traps, the cause is going to be JavaScript. Typically there is a function tied to the field being focused or activated. This can cause a race condition freezing the browser. More likely, there is function that prevents tabbing out, or the function tied to moving out is not firing.
Take the object where the keyboard trap is happening. Reproduce it locally, then start stripping back all that is tied to it. For example, if you are using custom dropdown, remove all the custom code. Begin with the base HTML <select> and <option> elements.
Is there still a keyboard trap? If you extracted all JS hooks and custom HTML, there should be no trap. Once we establish that the basic HTML works, let’s expose the custom HTML.
Hide any classes tied to JS functions. Remove data attributes. Get the JS out of the way. And try it again. Is it stuck now? Then it is time to examine out HTML again. No, then we slowly start adding in JS one item at a time until we find out trap.
Time to fix it
I cannot really tell you how long to remediate this would be. Everyone’s architecture is different and will cause different problems in different ways. But finding the trap’s location might take a day. Determining the cause could also take time, even for the most skilled developer. I recall early on spending 10 hours searching for an error in my code. It turned out to be the dreaded missing semicolon. It happens to all of us. Its about how do we fix it once we know of it.
Have questions? Come talk to me on LinkedIn or BlueSky!
