The Importance of Proper Form Validation and Meaningful Error Messages

Website form validation is a critical part of any online form, ensure your website visitors and customers have a good experience when trying to place orders or send enquiries.

This post was prompted by a recent experience with the Royal Mail postage website when trying to place orders for international postage and a very frustrating error message which did not tell me the actual issue and told me to contact customer support.

The error message stated: “An unexpected error occurred while processing the order. Please contact our support team.”

After two days of not being able to send a customer's order, email support told me that the customer's EORI (tax) number was too long causing the page to fail.

Forms are a crucial part of most websites. From signing up for a service, making a purchase, or submitting an enquiry, users interact with forms all the time.

Poorly validated forms with unhelpful error messages can lead to frustration, abandoned processes, and lost customers. It is essential to validate forms correctly and provide clear, relevant error messages.

This highlights a common issue with website forms not limiting the inputs to the maximum length accepted or not showing friendly and useful error messages to highlight the errors.

Why Form Validation Matters

1. Prevents Incorrect Data Submission

Without proper validation, users might submit incomplete or incorrect information, resulting in issues processing your visitors or customers' data. For example, an email field without validation could result in an invalid email address being stored, making it impossible to contact the user.

2. Enhances User Experience

A well-validated form helps users complete tasks smoothly. When errors are caught early and explained clearly, users can quickly correct mistakes rather than feeling confused or frustrated.

3. Improves Security

Forms are a common entry point for malicious attacks, such as SQL injection or cross-site scripting (XSS). Proper validation helps prevent harmful input, protecting both the website and its users.

4. Reduces Customer Support Requests

If users struggle to complete a form due to vague error messages, they may contact support for help or give up entirely going to a competitors website or service. Clear, specific validation reduces unnecessary support queries and increases form completion rates.

The Problem with Generic Error Messages

Imagine entering your information on a form and encountering an error message that simply says, “Something went wrong” or “Invalid input.” This is frustrating because it doesn’t tell you what the actual problem is or how to fix it.

Instead, error messages should:

1. Be specific – Clearly state what is wrong (e.g., “Please enter a valid email address” instead of “Invalid input”).
2. Highlight the problem – Indicate which field needs correcting.
3. Offer guidance – Suggest how to fix the issue (e.g., “Your password must be at least 8 characters long”).

Best Practices for Form Validation and Error Messaging

1. Validate on the Client and Server Side

Client-side validation (e.g., using JavaScript) provides instant feedback, while server-side validation ensures security and accuracy.

2. Use Inline Validation Where Possible

Instead of making users submit a form before seeing errors, validate fields as they are filled out. This saves time and reduces frustration.

3. Make Error Messages Easy to Understand

Avoid technical jargon or vague statements. Instead of “Invalid field,” say “The phone number must include only digits.”

4. Highlight Errors Clearly

Use colours (such as red) and icons to draw attention to fields with errors. Ensure users with visual impairments can still understand the message.

Many CSS frameworks such as Bootstrap have form validation styles to easily highlight any incorrect form fields.

5. Don’t Rely Solely on Colour

Users with colour blindness may struggle if errors are indicated by colour alone and include text explanations alongside any visual cues.

6. Provide Real-Time Feedback

If a user enters an invalid email format, let them know immediately rather than waiting until they submit the form.

7. Preserve User Input

If a form submission fails, don’t clear or delete the fields data. Retain the user’s input so they don’t have to start again.

Proper form validation and useful error messages can significantly improve user experience, reduce frustration, and enhance security. By clearly indicating errors and providing helpful guidance, websites can ensure users complete forms accurately and efficiently.