Table 2.

Usability Heuristics for User Interface Design.

Heuristica	Definition	Questionnaire items
Visibility	The system should always keep users informed about what is going on, through appropriate feedback within a reasonable amount of time.	“Does every screen begin with a title or header?” “It is obvious to the user what is going on?” “Is the font large enough?”
Match between system and real world	The system should speak the users’ language, with words, phrases, and concepts familiar to the user, rather than system-oriented terms. Follow real-world conventions, making information appear in a natural and logical order.	“Are menu choices and information ordered in a logical way?” “Do related and interdependent information appear together?” “Is language clear and concise (terminology familiar to users)?”
Consistency	Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions.	“Does the app use a minimal number of colors (i.e., color consistency)?” “Is there a consistent design scheme across the app?” “Do online instructions/information appear in a consistent location across screens?”
User control and freedom	Users often choose system functions by mistake and will need a clearly marked “emergency exit” to leave an unwanted screen without having to go through an extended dialogue. Support “undo” and “redo” actions.	“Is there navigation on the homepage of the app?” “Can users easily reverse their actions?” “Is the app explore-able and easy to navigate?”
Error prevention	Even better than good error messages is a careful design that prevents a problem from occurring in the first place. Either eliminate error-prone conditions or check for them and present users with a confirmation option before they commit to an action.	“Are menu choices logical, distinctive, and mutually exclusive?” “Are buttons/commands placed a good distance from one another?” “Does the system prevent users from making errors whenever possible?”
Recognition rather than recall	Minimize the user’s memory load by making objects, actions, and options visible. The user should not have to remember information from one part of the dialogue to another. Instructions for use of the system should be visible or easily retrievable whenever appropriate.	“Are instructions visible?” “Is it obvious what is clickable?” “Does the app require high levels of concentration?”
Flexibility and efficiency of use	Accelerators—unseen by the novice user—may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users. Allow users to tailor frequent actions.	“Does the app provide function keys for high-frequency commands?” “Does the app allow for customization (e.g., settings, search)?” “Does the app provide customization for frequency users (e.g., log in, saves data)?”
Aesthetic and minimalist design	Dialogues should not contain information that is irrelevant or rarely needed. Every extra unit of information in a dialogue competes with and diminishes the visibility of relevant information.	“Is the layout clearly designed avoiding visual noise?” “Does the use of images and multimedia content add value?” “Are images well sized and is the resolution appropriate?”
Error recovery	Error messages should be expressed in plain language (no codes), precisely indicate the problem, and constructively suggest a solution.	“Are there error messages?” “Is sound, images, or haptics used to signal an error?” “Are error messages worded so the user understands the problem and what to do next?”
Help and documentation	Ideally, the system can be used without documentation, but in the case of questions or confusion, it’s important to provide help and documentation. Any such information should be easy to search, focused on the user’s needs, list concrete steps to be carried out, and not be too lengthy.	“Are there instructions/help/documentation?” “Are navigation and instructions easy to find?” “Are navigation and instructions procedural (how do I use the app)?”