Bad value “” for attribute “maxlength” on element “textarea”: The empty string is not a valid non-negative integer.

The maxlength attribute controls the maximum number of characters a user can type into a <textarea>. According to the HTML specification, its value must be a valid non-negative integer — that is, a string of one or more ASCII digits like 0, 100, or 5000. An empty string (""), whitespace, negative numbers, or non-numeric values are all invalid. When the browser encounters an invalid maxlength value, its behavior becomes unpredictable — some browsers may ignore the attribute, while others may silently enforce no limit, leading to inconsistent form behavior across platforms.

This issue frequently arises when a server-side template or JavaScript framework conditionally outputs the maxlength attribute but produces an empty value when no limit is configured. For example, a template like maxlength="{{ maxChars }}" will render maxlength="" if the maxChars variable is empty or undefined. The fix is to ensure the attribute is omitted entirely when no value is available, rather than rendering it with an empty string.

Omitting maxlength allows unlimited input. Setting it to 0 is technically valid but prevents the user from entering any characters at all, which is rarely useful. Choose a value that makes sense for your use case, such as the corresponding database column’s character limit.

Why this matters

• Standards compliance: The HTML specification explicitly requires a valid non-negative integer. An empty string violates this rule and produces a validation error.
• Consistent behavior: Browsers handle invalid attribute values differently. A valid value ensures the character limit works reliably across all browsers.
• Accessibility: Screen readers and assistive technologies may announce the maximum character limit to users. An empty or invalid value could cause confusing announcements or be silently ignored.
• Form reliability: If your application depends on maxlength for client-side input restrictions (e.g., to match a database column limit), an invalid value means the constraint isn’t enforced, potentially leading to data truncation or server errors.

How to fix it

1. Set a specific integer value if you need a character limit: maxlength="200".
2. Remove the attribute entirely if no limit is needed. An absent maxlength means unlimited input.
3. Fix your templates — if you’re using a server-side language or JavaScript framework, conditionally render the attribute so it’s omitted when no value is provided rather than output as empty.

Examples

❌ Invalid: empty maxlength value

The empty string is not a valid non-negative integer, so this triggers the validation error.

<label for="msg">Message</label>
<textarea id="msg" name="message" maxlength=""></textarea>

❌ Invalid: non-numeric maxlength value

Strings, decimals, and negative numbers are also invalid.

<label for="bio">Bio</label>
<textarea id="bio" name="bio" maxlength="none"></textarea>

<label for="notes">Notes</label>
<textarea id="notes" name="notes" maxlength="-1"></textarea>

✅ Fixed: specific integer value

Set maxlength to the desired character limit.

<label for="msg">Message (max 200 characters)</label>
<textarea id="msg" name="message" maxlength="200"></textarea>

✅ Fixed: attribute omitted entirely

If no character limit is needed, simply remove the attribute.

<label for="msg">Message</label>
<textarea id="msg" name="message"></textarea>

✅ Fixed: conditional rendering in a template

If you’re using a templating engine, conditionally include the attribute only when a value exists. The exact syntax depends on your framework — here’s a conceptual example:

<!-- Instead of always outputting the attribute: -->

<!-- <textarea maxlength="{{ maxChars }}"></textarea> -->


<!-- Only render it when maxChars has a value: -->

<!-- {% if maxChars %}<textarea maxlength="{{ maxChars }}"></textarea>{% endif %} -->


<label for="feedback">Feedback</label>
<textarea id="feedback" name="feedback" maxlength="500"></textarea>

Learn more:

MDN Reference

<textarea>: The Textarea element - MDN

→

MDN Reference

maxlength - HTML attribute: MDN

→