Change on Request
Changes of context are initiated only by user request, or a mechanism is available to turn off such changes.
In plain language
Any significant change — like opening a new page, a new window, or submitting a form — should only happen when the user explicitly asks for it, or there should be a way to turn off automatic changes.
Why it matters
An unexpected change of context can disorient anyone, but it's especially disruptive for people with cognitive disabilities or screen reader users, who may not immediately understand what just happened or why. Requiring an explicit action (or offering an opt-out) keeps people in control.
In practice
Fails this criterion
A form automatically submits the moment the user selects an option from a dropdown, with no explicit submit button and no way to prevent this.
Meets this criterion
The same form has a clear "Submit" button — nothing happens automatically just from selecting an option.
Test it yourself
Interact with the site's forms and controls. Does anything significant (a new page, a submission, a new window) happen automatically, without you explicitly clicking a button to confirm it? If so, this criterion is failing.