How to Limit Character and Number Length in WooCommerce Checkout Fields

Many WooCommerce store owners need to limit the number of characters or digits customers can enter into specific checkout fields. This is a common requirement for phone numbers, gift messages, order notes, addresses, or custom fields where space is limited, such as on physical gift cards or in digital invoice systems.

Based on community discussions, a frequent point of confusion is the difference between a field's visual maxlength attribute and full server-side validation. While the maxlength attribute can prevent typing beyond a limit, it can often be bypassed by pasting text or through browser extensions. True validation requires both a frontend limit and server-side checks to ensure data integrity before an order is processed.

Common Solutions for Field Length Validation

There are a few primary methods to achieve character or number limits, depending on your setup and technical comfort level.

1. Using the 'Checkout Field Editor' Plugin (Pro Version)

Analysis of support threads indicates that advanced validation options, such as setting minimum length, maximum length, or specific character patterns (e.g., Latin characters only), are features typically found in the Pro version of the 'Checkout Field Editor (Checkout Manager) for WooCommerce' plugin. The plugin's team has stated in numerous responses that these specific validation features are not available in the free (lite) version. If your business critically depends on robust and easily configurable field validation, investigating the Pro version's capabilities may be the most straightforward solution.

2. Custom Code for Basic Validation (Advanced Users)

For those comfortable with code, WooCommerce provides hooks to add custom validation. This method requires adding code to your theme's functions.php file or a site-specific plugin.

The most relevant hook for this task is woocommerce_after_checkout_validation. This hook allows you to check the values of all checkout fields after the user submits the order but before it is processed. You can validate the length of a specific field and return an error if the limit is exceeded.

Example Code Snippet:
The following example demonstrates how to limit the 'order_comments' field to 20 characters.

add_action('woocommerce_after_checkout_validation', 'thw_validate_order_notes_length', 10, 2);

function thw_validate_order_notes_length($data, $errors) {
    // Get the value of the order comments field
    $order_notes = isset($data['order_comments']) ? $data['order_comments'] : '';
    
    // Check if the length exceeds 20 characters
    if (strlen($order_notes) > 20) {
        // Add a validation error, preventing checkout from proceeding
        $errors->add('validation', 'Order notes cannot exceed 20 characters.');
    }
}

Important Notes on Using Custom Code:

• This code only adds server-side validation. For a better user experience, you may also want to add a maxlength attribute to the field's HTML input to provide immediate feedback. This often requires additional code.
• Always use a child theme when modifying theme files to prevent your changes from being overwritten by updates.
• Test any code thoroughly on a staging site before implementing it on your live store.

Conclusion

Implementing character limits on WooCommerce checkout fields is a common need with a few different paths to a solution. The best choice depends on your technical expertise and specific requirements. For a code-free, fully featured solution with a user interface, the Pro version of a dedicated field editor plugin is often the recommended route. For developers or those with simpler needs, custom validation using WooCommerce hooks provides a flexible, albeit more technical, alternative.