App Usability Guidelines & Survey

Please read through the guidelines below and provide feedback using the brief survey at the end.

App Usability (U) Guidelines
The Usability Guidelines assess how a mobile health app is designed to be safe and easy to use by incorporating five key quality aspects of usability: learnability, efficiency, memorability, prevention of errors, and user satisfaction. Apps designed based on sound usability principles will be optimized for use by the specified users within the specified use environments.

Guideline U1 Visual Design
Apps should follow standards of visual design that promote legibility, clarity of content, and user engagement without introducing unnecessary distraction. Apps that leverage user expectations in their design strategy shorten the learning curve and decrease user frustration.

Performance Requirements for Guideline U1

  • 01 App layout should be adaptable such that usability and functionality do not differ between landscape or portrait mode. Ideally, interfaces should be flexible to operate in both orientations.
  • 02 Usability of app content should be consistent across a variety of mobile screen sizes and operating systems.
  • 03 Screen colors should provide contrast so users can easily distinguish between the different elements on the screen, with an emphasis on distinction between the content and background.
  • 04 Color should not be used as the only identifier of critical or safety-related information . At least one redundant cue, such as an icon, label, or other text, should be provided.
  • 05 Extraneous text, graphics, and animation should be used sparingly. Information that is actively populating should serve a purpose and avoid distracting the user or cluttering the screen if only for aesthetic purposes.
  • 06 Important elements critical to app functionality and content understandability should be positioned above the scroll line to minimize the opportunity for missed information. Users should be able to clearly identify when screens extend beyond the scroll line.
  • 07 App design should provide clear indications that elements are actionable. Interactive elements can be differentiated from non-selectable content through design choices that should be used consistently throughout the app (i.e., color, text style).
  • 08 App design should support recognition over recall by keeping relevant information on screen rather than forcing users to remember it.
  • 09 When possible, reduce the probability of data entry error by providing users with selectable options rather than requiring text entry.
  • 10 Selectable items should be a minimum of 7 to 10 millimeters in length and width, with appropriate spacing allowance between items to avoid unintended selections.

Guideline U2 Readability
Text used within the app must be readable, understandable, and adjustable to accommodate ease of operation for a variety of devices, users and use environments. Text size adjustments should not alter the screen layout in a manner that could confuse users or prohibit ease of use.

Performance Requirements for Guideline U2

  • 01 The default font size for paragraph text should follow the minimum standard guidelines for the platform of use (e.g., 17pt for iOS, 14sp for Android).
  • 02 Different font sizes should be utilized to establish text hierarchy, with larger font sizes signifying headers and smaller font sizes used for paragraph text.
  • 03 Apps should avoid presenting information in paragraph form when possible. When large amounts of information must be displayed, implement information chunking (i.e., intuitive grouping) or utilize lists and tables to facilitate learnability and memorability.
  • 04 Text should incorporate appropriate spacing allowance between lines (e.g., 1.2 times the font height) to allow for breathability and readability.
  • 05 Content should be written at reading level appropriate for the user population. Language for lay users without clinical knowledge should be written at or below a sixth-grade reading level.
  • 06 Text should avoid use of jargon or acronyms that may not be familiar to users, particularly for lay users without clinical knowledge.

Guideline U3 App Navigation
Users should be able to navigate quickly and easily between screens to complete tasks. Navigation should feel natural and familiar, and should not dominate the interface or draw focus away from content.

Performance Requirements for Guideline U3

  • 01 Users should be able to easily identify where they are in the app and how to navigate to different destinations. The navigational path should be logical, predictable, and easy to follow. For screens that users may need to access in succession, providing shortcuts may improve ease of navigation.
  • 02 Minimize the number of taps, swipes, or screens required to navigate from one area of the app to another.
  • 03 App design should facilitate reversible actions by allowing the user to navigate back to previous pages.
  • 04 Menu options should be labeled intuitively such that users can easily locate information within the app. Users should not have to locate information by trial and error.
  • 05 The app’s main menu should be easily locatable and identifiable. Standard app design conventions would likely lead most users look for a menu on the top, left-hand side of the screen. A collapsed menu is often associated with the three-bar “hamburger” icon that frequent app users are expected to be familiar with.

Guideline U4 Onboarding
Apps should facilitate an intuitive process for launching, registering, entering personal information (if applicable), and preparing for first-time use. As the users’ first introduction to the app, a simple and intuitive onboarding process is critical in instilling user confidence that the app will provide a satisfying overall user experience.

Performance Requirements for Guideline U4

  • 01 The app provides a launch screen that clearly identifies the name and purpose of the app, and gives the user intuitive options for initiating use.
  • 02 Provide the user with opportunities either to access detailed instructions and product information or to bypass this and immediately begin app setup.
  • 03 Users should be allowed to bypass entry of personal data if it is not critical for app functionality. Data that is needed for the app to work as intended (e.g., alert and notification parameters) should be mandatory to avoid inaccurate app behavior.
  • 04 For apps with complex onboarding processes, entered data should be stored so that users can recover and avoid reentry if they are disconnected during the onboarding process.
  • 05 When setup is complete, provide options for a walkthrough or tutorial on app use.
  • 06 Apps should bypass onboarding for returning users, but allow users to update the data entered during onboarding at any time through intuitively named menu selections (e.g., Profile, Settings).

Guideline U5 App  Feedback
Apps should provide sufficient feedback to inform the user of the results of their actions and promote understanding of what is going on in the system. Feedback includes app reactions to user input, including providing messages to the user. Efficient and informative feedback ensures that users will be able to understand and perceive app actions without frustration. Guidelines associated with feedback related to notifications, alarms, and alerts can be found within Guideline U6.

Performance Requirements for Guideline U5

  • 01 Feedback messages should appear in an expected and consistent location within the interface so that they are noticeable to the user (e.g., near the input location).
  • 02 Feedback messages that are not urgent or associated with a safety risk should be unobtrusive to app operation.
  • 03 Ongoing processes (e.g., loading) should utilize ongoing feedback to communicate status to the user. For longer processes such as downloading, inform the user of time remaining for the process to complete.
  • 04 Feedback should occur quickly such that users can detect that their actions were successful. Avoid excessive lag between the action and the result (e.g., the user selects a menu option and the app takes several seconds to open the new page).
  • 05 Error messages must, in clear and concise language understandable to the user, explain the problem and inform the user of the required corrective actions.
  • 06 Users should be informed of data entry requirements. For example, if a user needs to choose a password during the setup process that requires both letters and numbers, this information should be stated at the point of data entry rather than only in the form of an error message.

Guideline U6 Notifications, Alerts & Alarms  
Notifications (general reminders or updates to the user), alerts (non-urgent indicators intended to capture user attention), and alarms (urgent indicators that may be safety-critical) must consider both safety and usability to inform users when attention is required.

Performance Requirements for Guideline U6

  • 01 Safety-critical alarms should utilize redundant signals to the user (e.g., visual, audible, tactile). Users should be forced to acknowledge alarms before moving forward with other tasks.
  • 02 Users should be given the choice to opt out of non-critical notifications and alerts.
  • 03 Volume for audible notifications and vibration strength of tactile notifications should be customizable.
  • 04 Notifications, alerts, and alarms should be stored as historical data so they are available for reference. This also provides a secondary resource for the user if a notification is dismissed in error. If an app allows the user to dismiss alerts and requires the user to select a reason for dismissal, this data should also be stored.

Guideline U7 Help Resources and Troubleshooting
Apps must incorporate help and troubleshooting features to guide the user when needed. Unavailable or unclear help features may lead to user confusion, frustration, and ultimately app abandonment.

Performance Requirements for Guideline U7

  • 01 Apps should have an easy-to-locate help section that consolidates all information intended to assist the user.
  • 02 Help features and informational links should be imbedded in the app when users may be likely to need them. Pop-ups are more appropriate for simple information such as terminology definitions, while links to the help section can be used for more complex troubleshooting.
  • 03 Step-by-step walkthroughs should not be required for each completion of a task. Experienced users should be allowed to bypass detailed instructions.
  • 04 Instructional information should avoid text-heavy paragraphs and give users easy-to-follow lists of task steps. For more complex processes, incorporate graphics or videos to supplement and/or replace text.

Guideline U8 Historical Data 
Apps used to gather data should store historical data in a manner that is easy for users to access and understand.

Performance Requirements for Guideline U8

  • 01 For large data repositories, historical data should be sortable and filterable. Data sets for clinical-use apps that contain historical data for multiple patients should clearly identify patient name or ID.
  • 02 Users should be informed if apps have a limited amount of data storage. Notifications may be used if an app will delete data after a specified amount of time.
  • 03 Historical data should be displayed in a manner intuitive to the user and customized depending on the type of data (e.g., chronological, alphabetical). For example, an app that collects daily data from a user might present historical data in reverse chronological order so that a user has easy access to the most recent data collected.

Guideline U9 Accessibility

Apps should be designed and built to accommodate a wide variety of users, including those with disabilities such as perceptual impairment (visual or auditory), cognitive impairment and learning disabilities, and motor impairment. Designs that are made to be adaptable will facilitate ease of use for all users, not just those with disabilities. Additionally, app design should aim to accommodate use with common assistive technologies (e.g., screen readers).

Performance Requirements for Guideline U9

  • 01 App content should be adaptable and accessible for a variety of users. For example, provide text alternatives for multimedia (e.g., descriptions of images) or captions for video content and other alternatives. Content should be tailored such that it is presentable in either an audio or visual format without losing meaning.
  • 02 Content layout should consider screen reader accessibility. This includes providing screen reader accessible alt text for images, and labels for buttons, icons, and loading states.
  • 03 Apps should aim to accommodate a variety of input modalities, including gestures or use of an external keyboard. The content should not limit the user’s interaction to any specific input unless it is essential or to ensure security of content.
  • 04 To the extent possible, app design should facilitate one-handed use.
  • 05 Alternative input modalities, such as speech recognition, gestures, and handwriting recognition, may produce results that are less “exact” than standard input methods. These input modalities should require the user to validate inputs (e.g., through use of confirmation screens or providing undo/redo options) so that unwanted actions are avoided.
  • 06 Content should retain functionality and readability when adjustments are made to accommodate accessibility.

Guideline U10 On-Going App Evaluation
Throughout the entire development lifecycle, apps should undergo robust, iterative evaluations that follow a user-centered design process. Understanding the user perspective and evaluating technology to test assumptions is critical in developing safe and usable products, and apps that do not meet user expectations or are cumbersome to use are unlikely to be adopted. Apps requiring review by the Food and Drug Administration (FDA) should undergo testing evaluation that follows the FDA’s guidelines for applying human factors and usability engineering to medical device design.

Performance Requirements for Guideline U10

  • 01 Research on the target user population and anticipated use environments should be conducted to gather data on the characteristics of the app end users, whether clinical or laypeople, and assess how the environmental characteristics (e.g., noise, lighting, distractions) may impact safety and usability. This can be accomplished through activities such as ethnographic research, user interviews, and focus groups.
  • 02 The target user population should be well-defined before initiating additional user activities (e.g., interviews, user testing). Evaluations should focus primarily on gathering data from those who fit the characteristics of expected user populations. This helps to ensure that the relevant physical attributes, cognitive expectations, and specific experiences of the end users are accounted for in design.
  • 03 Apps intended to be used in a clinical environment should incorporate design elements that consider how the app may realistically fit into clinical workflow. Workflow assumptions should be reevaluated regularly to accommodate changes in current practices.
  • 04 Apps should be designed to meet known usability heuristics. Trained human factors or usability specialists should be engaged to conduct heuristic evaluations using validated heuristic sets as part of usability assessment during the development process.
  • 05 Apps should utilize tools such as failure modes and effects analysis or fault tree analysis to determine what if there are user tasks that could present risk to the patient or user. Apps should be designed to reduce or eliminate risk.
  • 06 User testing should be conducted iteratively with the target end users of the app. User tests should produce both quantitative data on performance of app tasks, as well as qualitative feedback from study participants. Data gathered in the formative stages should be used to generate design updates that are expected to improve safety and usability.
  • 07 A final summative (validation) test should be conducted to ensure the app can be used safely and successfully. The summative test should evaluate the major usage scenarios that a user is expected to encounter, and include evaluation of any user tasks that could have safety implications. A minimum of 15 users per distinct user group should complete the summative test to detect 90% of potential usability challenges.


ISO 9241-11:2018 Ergonomics Of Human-System Interaction – Part 11: Usability: Definitions And Concepts

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