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How to use the required attribute in HTML5 forms? (Validation Example)
How to use the required attribute in HTML5 forms? (Validation Example)
The required attribute in HTML5 enforces mandatory form fields without JavaScript by using a boolean flag; it works with input, select, and textarea elements, triggers browser validation on empty submission, supports CSS pseudo-classes like :required and :invalid, and pairs with other attributes (e.g., email, min, pattern), though server-side validation remains essential.
The required attribute in HTML5 is a simple yet powerful way to enforce that a user must fill out a form field before submitting. It’s a boolean attribute — meaning its mere presence (no value needed) tells the browser this field is mandatory.
How to add the required attribute
Add required directly to an input, select, or textarea element. No value is necessary — just include the word “required”:
<input type="text" name="username" required><select name="country" required><option value="">Choose</option></select><textarea name="message" required></textarea>
How browser validation works
When a form with a required field is submitted and that field is empty, the browser automatically prevents submission and shows a native tooltip or message (e.g., “Please fill out this field”). This happens without JavaScript — it’s built into modern browsers.
Note: The field must have a non-empty value. For inputs like text or email, whitespace-only entries usually count as empty. For <select></select>, the first option should have an empty value="" to trigger validation properly.
Styling invalid fields with CSS
You can visually highlight required fields or show errors using pseudo-classes:
input:required { border-color: #007bff; }input:invalid { border-color: #dc3545; }input:valid { border-color: #28a745; }
These styles apply based on whether the field meets its constraints (including required). Use :user-invalid for more precise control after user interaction.
Combining required with other attributes
required works well alongside other validation attributes:
-
<input type="email" name="email" required>— ensures both non-empty and valid email format -
<input type="number" name="age" min="18" required>— requires a number ≥ 18 -
<input type="text" name="city" required pattern="[A-Za-z\s]{2,}" title="City name must be at least 2 letters">— adds custom pattern matching
Remember: client-side validation like required improves UX but never replaces server-side checks — always validate on the backend too.
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