About Required Marks in Input Forms

I have summarized information about the “required” mark in overseas screen UI (forms), along with UI guideline materials.

📌 Main Required Marks and Best Practices

Using an Asterisk (*)
- This is generally the most widespread method, adding “*” to required fields.
- However, an explanation such as “* indicates a required field” at the beginning of the form is essential (Nielsen Norman Group, California State University, Northridge).
- There are also examples that use color for emphasis (such as red text).
Clearly Stating “Required” or “(required)” in the Label
- By explicitly adding “Required” in text within the label, it can be clearly communicated to screen readers, improving accessibility (Deque).
Using ARIA Attributes or HTML5 required Attribute in Conjunction
- In addition to visual indication, using aria-required="true" or <input required> allows you to programmatically communicate that a field is required (Deque).
Clearly Stating Optional Fields Using “(optional)”
- There is also a method of explicitly indicating optional fields as “(optional)” instead of required fields, which is effective when both are mixed.
- However, Nielsen-Norman points out that “it is easier to judge if required fields are also explicitly indicated” (TPGi).

✅ Summary of UI Guideline Materials

Source	Content
NN/g: Marking Required Fields in Forms	A combination of an asterisk + explanatory text is recommended, and showing only optional fields is evaluated as unfriendly (Nielsen Norman Group).
Deque (Anatomy of Accessible Forms)	- Use the string “Required” or an image within the label. - Explicitly states that suggesting by color alone is insufficient.
W3C Techniques (H90)	There are examples of including an asterisk or “(required)” in the label and defining the meaning at the beginning of the form.
TPGi (Doing what’s required)	Considering accessibility, evaluated that an asterisk + ARIA attribute + inserting label text is optimal.
Contensis UX Forms Guidelines	Briefly summarizes that consistent marking (* or (optional)) is important.

✅ Recommended Implementation Approach

Add an explanatory text at the beginning of the form:
Fields marked with * are required. (Or collectively “All fields are required”, and if there are optional fields, “unless marked optional”)
Applying Labels:
- Write it like First Name * or Email (required).

ARIA Attributes / HTML5 Attributes:

1
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<label for="email">Email <abbr title="required">*</abbr></label>
<input id="email" required aria-required="true">

Do not rely on color alone: Support both visual and programmatic indications.

🔗 Reference Links (UI Guideline Materials)

NN/g: Marking Required Fields in Forms (California State University, Northridge, Nielsen Norman Group, Deque)
Deque: Anatomy of Accessible Forms (Deque)
W3C Techniques: H90 Indicating required form controls (W3C)
TPGi: Indicating mandatory fields accessibly (TPGi)
Contensis: UX Forms Guidelines (Contensis)

If necessary, I can also provide specific HTML/CSS code examples, UI component design templates for Sketch/Figma, etc. Please feel free to consult with me!