Usability standards and heuristics¶

Exercise usability-heuristics-annex.pdf · PDF

You tap "Pay" in a shopping app. Nothing moves. No spinner, no message. Did it work? Do you tap again and risk paying twice? That little moment of panic is not bad luck — it is a design mistake, and it has a name.

Designers have spent decades writing down what makes an app easy or painful to use. In this page you get their two most famous toolkits: Nielsen's 10 heuristics, the checklist designers use every day, and ISO 9241, the international standard that defines what "easy to use" even means.

What is usability?¶

Usability is the extent to which a system, product or service can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use.

That is the official definition from ISO 9241-11:2018. It sounds heavy, but it hides three simple questions:

Notice the word "specified", four times. Usability is never absolute: an app can be perfect for a 17-year-old on a phone and terrible for their grandmother on a tablet. Always ask who, to do what, and where.

Heuristics vs. standards¶

A heuristic is a rule of thumb: a short, practical rule that works most of the time, without being a strict law.

A standard is an official document, agreed by experts and published by an organization such as ISO (International Organization for Standardization), that many people follow so things work the same way everywhere.

You need both. Heuristics are your pocket checklist; standards are the rulebook behind it.

Nielsen's 10 usability heuristics¶

In 1990, Jakob Nielsen and Rolf Molich wrote a list of principles for interface design. Nielsen refined it into the famous 10 heuristics in 1994, and his company, the Nielsen Norman Group, last updated the wording in 2020. More than thirty years later, designers all over the world still use it almost unchanged.

To remember them, picture a good waiter in a restaurant. A good waiter does exactly what a good interface does: keeps you informed, speaks your language, lets you change your mind, and fixes problems politely. We will keep the waiter all through this section.

Go back to the "Pay" button from the start. Which heuristic did it break? Number 1: the app did not show its status. A spinner and a "Processing payment..." message would have saved you the panic.

How designers use the heuristics¶

A heuristic evaluation is a review where evaluators judge an interface against a set of heuristics to find usability problems.

It is cheap and fast: no users, no lab, just the checklist and the app.

flowchart LR
    A["<b>1. Pick the task</b><br>e.g. buy a ticket"] --> B["<b>2. Walk through it</b><br>screen by screen"]
    B --> C["<b>3. Check each screen</b><br>against the 10 heuristics"]
    C --> D["<b>4. Write each problem</b><br>where + which heuristic"]
    D --> E["<b>5. Fix the worst first</b>"]

The Nielsen Norman Group recommends that three to five people evaluate independently, because any single evaluator, however expert, misses some problems. Then they put their lists together.

ISO 9241: the official rulebook¶

ISO 9241 is a family of standards called Ergonomics of human-system interaction. It started life in 1992 as rules for office work with computer screens, and has grown into dozens of parts. Two matter most to you:

The seven interaction principles of ISO 9241-110:2020 will sound familiar — many overlap with Nielsen:

User engagement is new in the 2020 edition — a sign that standards now care about how an app feels, not only whether it works.

Key takeaways¶

• Usability = effectiveness + efficiency + satisfaction, for specific users, goals and contexts (ISO 9241-11:2018).
• A heuristic is a rule of thumb; a standard is an official, agreed rulebook. You use both.
• Nielsen's 10 heuristics (Nielsen and Molich, 1990; refined 1994) are the everyday checklist — think of a good waiter.
• A heuristic evaluation checks an app screen by screen against the heuristics, ideally with 3–5 evaluators.
• ISO 9241-110:2020 lists seven interaction principles, including the new user engagement.
• Pretty is not the same as usable: usability is about what people manage to do.

Quick check¶

Heuristics and standards apply to any interface. But when you design for an iPhone or a Mac, Apple has its own rulebook on top: the Human Interface Guidelines.