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HTML Academy · Lesson

required pattern min max and maxlength

Add built-in validation constraints to form inputs.

HTML5 Form Validation

HTML5 added built-in form validation — no JavaScript required:

  • Browsers check constraints before submitting
  • Native error messages appear automatically
  • Works with CSS :valid / :invalid pseudo-classes

required

The required attribute prevents submission if the field is empty:

<label for="email">Email (required)</label>
<input type="email" id="email" name="email" required>
<!-- Empty on submit → browser shows "Please fill in this field" -->
<!-- Also: field is :invalid until filled -->

All lessons in this course

  1. required pattern min max and maxlength
  2. The novalidate Attribute
  3. Constraint Validation API Basics
  4. HTML5 vs JavaScript Validation Trade-offs
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