This week we examined the Laws of UX again, this time – Postel’s Law.
Postel’s law, also known as the robustness principle, was formulated for TCP by John Postel.
Postel’s Law can best be described as designers being tolerant of any number of actions a user could possibly take within a product. For example, when a computer application receives input from the user, it should accept any range of input. Designers should accept variable input from users, translating that input to meet user requirements, defining boundaries for input, and providing clear feedback to the user.
Postel’s Law is useful to think about as a user interface designer, because if you design for a range of inputs, you can make your interfaces more robust and easy to use – which is helpful when it comes to the laws of usability. The law is also useful because it describes a very typical aspect of user experience. Users often find themselves at an unfamiliar website or application, attempting to find a way to accomplish their desired goals. So each user will navigate the product in a unique way. It also provides a framework for design to be consistent and reliable. Basically, Postel’s Law ensures products are tolerant to the variability of human inputs.
I can use Postel’s Law in my own work by designing interfaces to be tolerant of the range of inputs my users will give me. For example in a sign up form for my app prototype, I can make sure my email field accepts any alphanumeric combination of letters and numbers, and provide clear and obvious error messages.