The Giant List of Edge Cases

Designing for the “average” user? Turns out, there’s no such thing. The average user doesn’t exist.

When building your online surveys, user personas, empathy maps, customer journey maps, user requirement documentation, prototypes, and products—consider edge cases and biases.

Nail polish isn’t just for girls and women; some men wear nail polish. Not all bald people are men; some women shave their heads or lose their hair.

Call out stereotypes and biases whenever you find them. Be empowered to speak up and advocate for all users.

What’s an “edge case”?

An edge case is defined as an atypical, unusual, or rare circumstance or rate of occurrence.

The problem is—with 7.7 billion people on the planet (as of December 2019)—there’s really no such thing as “rare.” A circumstance that happens to “only” 0.1% people means it happens 7.7 million times. Or in the U.S., 329,000 people.

Failing to consider edge cases can result in lost customers, bad publicity, injury, or death.

What are some not-so-uncommon edge cases and biases to consider?

Whether conducting research or designing an online form, a mobile app, algorithm, or a physical product—consider the following edge cases and biases.

Note: I’ll continue to expand this list as I come across others to help rid the world of discrimination and poor accessibility. If you see edge cases or biases I’ve missed, please email me or tweet me @KristineRemer.

Privacy & Safety

A lot of people want to keep aspects of their lives private. Until given explicit permission, it’s best to keep gender, sexual identity, maiden name, hobbies, interests, place of employment, home address, children, and so on private.


  • An employee who is not “out” to co-workers or their employer
  • Someone who doesn’t want medical information or DNA leaked or stolen
  • Someone who is wary of fingerprint and facial scanning
  • Someone looking for another job, but doesn’t want their boss to know
  • Someone who wants to keep their hobbies to themselves
  • Someone who wants to keep their gift purchase or pregnancy secret

Also consider ways to protect your users’ safety.

  • Child custody battles where one parent might kidnap the child
  • An abused person hiding from their spouse / partner
  • Someone who wants to physically harm themselves or others
  • Someone who has been, or is about to be, assaulted
  • Someone who doesn’t want voicemails, texts, or mail that an abuser may see
  • Bullies, predators, stalkers, and harassers
  • Undocumented immigrants who are afraid to share information
  • User-friendly privacy policies and user agreements written in plain language

Gender / Sex

When asking for gender or sex on a survey, online form, or questionnaire, ask yourself (or team) if and why this question is necessary. Knowing that 80% of women use your product may invite bias and stereotypical thinking, and push out the very edge cases we want to include.

  • Women! Women are CEOs, doctors, and construction workers
  • People who identify as a different sex from their birth certificate
  • Non-binary people (i.e., people who don’t identify as any gender)
  • Gender fluid people


I am so, so happy that “they” is finally and officially recognized as a singular pronoun. Early in my writing career, I constantly used “they” in effort to be inclusive, and my editors would ALWAYS cross it out and write “he/she.”

Consider that some people may want to include their preferred pronoun on their name tag, when registering for events or conferences, or on their public profile. Is there a spot for “preferred pronoun” in your CRM or online form?


  • Mx. for those who want to use a title, but wants to be gender neutral
  • Mrs. can be used by divorced or widowed women, too

First, Middle & Last Names

  • No first name
  • No last name
  • No middle name
  • Hyphenated first, middle, or last name
  • 2 or more word first, middle, or last names (i.e., allow for spaces!)
  • Special characters (e.g., cedilla, umlaut)
  • Single letter first name, middle or last name
  • Preferred name (i.e., not their legal name)
  • Native American names (e.g., Running Bear)


  • City or town that is not the same as the ZIP code’s city / town
  • Apartment number, suite number
  • Apartment number, suite number is a fraction
  • No permanent address or homeless
  • Lives on a military base in the U.S. or another country

International addresses:

  • House number comes after street name
  • Long ZIP / postal codes
  • States, provinces, departments, regions
  • Larger cities may have designated neighborhoods

Race / Ethnicity

See Gender / Sex above. Be wary. Collecting this data may unintentionally invite in stereotyping, bias, or racism.

Hispanic refers to language, Latinx refers to origin. Also, the gender-neutral Latinx (vs. Latino or Latina) is becoming more common.

  • Belongs to 2 or more races or ethnicities
  • Doesn’t know race or ethnicity (or what to select)
  • Skin color comes in a wide range of pigments: very light to very dark (i.e., soap and towel dispenser sensors that don’t recognize dark skin)

Language & Culture

Consider the user’s native or preferred language when leaving voicemails, creating self-service phone trees, voice detections, and so on. When offering interpreter services, ensuring there are protocols and best practices in place.

Also, be aware of culture differences. For example, assigning emotions to a numerical Likert scale (in a survey or medical exam room) is confusing to some cultures.

  • Symbols & icons (e.g., not knowing what a stand mixer is)
  • Accents
  • Non-English speakers
  • English as a second language
  • Immigrants & refugees
  • Undocumented immigrants
  • Tourists from other countries


  • Unknown mother
  • Unknown father
  • Parental guardian
  • Parents are divorced / separated living separately
  • Parents are divorced / separated living together
  • Parent is deceased
  • Parents are same-sex
  • Parents are living together, but not married
  • Parent’s last name is not the same as child’s last name


  • Older parents living with children
  • Adult children living with parents
  • Grandchildren living with grandparents
  • Unrelated roommates

Spouse / Partner

  • Same-sex spouse or partner
  • Non-binary spouse or partner

Birthdays & Holidays

  • Not all people or religions celebrate birthdays
  • Not all people or religions celebrate Christmas or other holidays

Phone Numbers

  • No landline phone number
  • No cell phone number
  • Cell phone cannot receive text messages (or must pay for each one)
  • Non-U.S. phone number
  • Extension number

Email Addresses

  • No email address
  • Email address includes a country code suffix (e.g., au, ca)

Internet Access

  • No Internet access
  • No reliable, high-speed Internet access
  • Not technically-savvy (i.e., doesn’t know how to use a trackpad, webcam)

Social Media Usage

Not everyone has or wants to use their social media account to access your product. Allow people to sign up for your product or service using an email address, phone number, or alternate method.


Be sensitive to information, images, and purchases that users have shared. Facebook is famous for using user images in very inappropriate and insensitive ways (e.g., celebrating a child’s death, a painful divorce).

Payment Method

  • No credit card
  • Doesn’t carry cash

Seeing, Hearing, and Speaking

Consider contrast, point sizes, transcriptions for both video and in real-time for live events, screen readers, and cultural differences for symbols.

Take the time to professionally caption all videos. A transcript or using AI to auto-caption isn’t cutting it. 100% of your users benefit from quality captioned videos, not just those with difficulty hearing.

  • Not able to see, hear, or speak
  • Difficulty seeing, hearing, or speaking
  • Color blind
  • Doesn’t have access to computer speakers or headphones
  • Doesn’t speak English or cannot read the translations provided
  • Has dyslexia or other reading difficulty
  • Cannot read or reads at a lower reading level

Motor Skills

  • Unable to walk or has difficulty walking (e.g., uses wheelchair, cane, scooter, walker)
  • Unable to use or has difficulty using hands or fingers (e.g., arthritis, carpal tunnel syndrome, amputation, third degree burns)
  • No finger print(s)
  • Unable to or has difficulty bending (e.g., arthritis, recent surgery)
  • Carrying a child, bag of groceries, or other heavy object while multi-tasking
  • Left-handed

Cognitive Skills & Health Conditions

There are too many to list, but consider that parents or caretakers may be using your “designed for a child” product for their adult child or adult patient, too. Consider those susceptible to seizures.

For More Information

If you’re looking for more edge case stories or case studies, I highly recommend Sara Wachter-Boettcher’s book, “Technically Wrong: Sexist Apps, Biased Algorithms, and Other Threats of Toxic Tech.”

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Author: Kristine Remer

June UX is led by Kristine Remer, a CX / UX research and strategy consultant in Minneapolis. She helps companies drive significant business outcomes by finding and solving customer problems. When she's not creating customer journey maps and conducting diary studies, Kristine is either kayaking or watching her kids play soccer.