5 Ways to Implement 10-Digit Phone Number Validation in HTML

Validating 10-digit phone numbers in HTML is a common requirement for ensuring data quality. We'll explore five ways to implement this check, complete with code snippets. We will also look at the limitations of these client-side methods and see how Abstract API provides a more robust solution.

HTML Phone Number Validation Methods

Here are four common methods to validate 10-digit phone numbers directly in HTML. Each approach uses different built-in browser features or simple client-side scripts to enforce the format.

Native Pattern and Length Attributes

The input element with type tel allows for native browser validation without JavaScript. You can use several attributes to enforce a 10-digit number format. These attributes leverage the browser’s built-in constraint system, so the field participates in form-level validity.

• pattern: This attribute supplies the regular expression that the input value must satisfy. For a 10-digit number, this would be \d{10}.
• minlength/maxlength: These attributes provide an additional numeric guard. The browser blocks input outside of this character range, and the field will fail validation.

<input
  type="tel"
  name="phone"
  inputmode="numeric"
  pattern="\d{10}"
  minlength="10"
  maxlength="10"
  title="10 digits, no separators"
  required>

Numeric Input with a Range

For cases where leading zeros are not a concern, the input type number offers a simple alternative. You can set a minimum and maximum value to define a numeric range that corresponds to 10-digit numbers.

The browser then automatically restricts the input to numbers between 1,000,000,000 and 9,999,999,999. The browser's validity state reflects any violations through rangeOverflow or rangeUnderflow properties, and no regular expression is needed.

<input
  type="number"
  name="phone"
  min="1000000000"
  max="9999999999"
  step="1"
  required>

Custom Validity with JavaScript

When you require more complex validation logic than attributes can provide, you can use JavaScript. The Constraint Validation API allows you to set a custom error message on an input field based on your own logic.

The script checks if the input matches a 10-digit pattern. If it does not, the setCustomValidity() method flags the field as invalid. This custom check integrates seamlessly with the form's overall validation process.

const field = document.querySelector('#phone');
const tenDigits = /^\d{10}$/;

field.addEventListener('input', () => {
  field.setCustomValidity(
    tenDigits.test(field.value) ? '' : 'Need exactly 10 digits'
  );
});

document.querySelector('form').addEventListener('submit', e => {
  if (!e.target.checkValidity()) e.preventDefault();
});

Input-Mask Library

An input-mask library can enforce a specific format as the user types, which improves the user experience. This approach uses a script to guide data entry and ensure the format is correct from the start.

The library applies a mask, like '999-999-9999', to the input field. It only permits digits and can submit the raw 10-digit number to the server upon form submission, which provides a clean data handoff.

<script src="https://unpkg.com/inputmask@5/dist/inputmask.min.js"></script>
<input id="phone" type="text" required>
<script>
  Inputmask({
    mask: '999-999-9999',
    removeMaskOnSubmit: true,
    onBeforePaste: p => p.replace(/\D/g,'')
  }).mask('#phone');
</script>

Challenges of HTML Phone Number Validation

Client-side validation presents several inherent limitations. These methods struggle with diverse user inputs, evolving numbering plans, and the nuanced rules that define a truly valid, routable phone number.

• The pattern attribute on an input field only supports basic regular expressions. This limitation prevents complex rules, like the exclusion of N11 service codes, which requires more advanced logic or extra JavaScript to enforce properly.
• Users often paste numbers with extra characters like parentheses, dashes, or a leading "1". HTML attributes like pattern or minlength cannot normalize this varied input, which leads to either false rejections or acceptance of improperly formatted data.
• A strict 10-digit rule is a North American convention and fails for international phone numbers. Methods like a fixed pattern or a numeric range create a rigid system that excludes valid global formats, which contradicts the free-form nature of telephone inputs.
• Real-world number validity changes over time as authorities reserve or reclaim area codes. A static HTML pattern cannot track these updates, so a number that passes client-side validation might still be invalid or unroutable in the real world.