If security concerns or other factors require a time limit to be enforced, users should be warned in advance before the time limit expires and offered an opportunity to extend their time.
The following are among the techniques recommended by the W3C Web Content Accessibility Guidelines 2.1:
- Turn off: The user is allowed to turn off the time limit before encountering it
- Adjust: The user is allowed to adjust the time limit before encountering it over a wide range that is at least ten times the length of the default setting
- Extend: The user is warned before time expires and given at least 20 seconds to extend the time limit with a simple action (for example, “press the space bar”), and the user is allowed to extend the time limit at least ten times