HTML Guides for max

The max attribute defines the maximum value that is acceptable and valid for the input containing it. When the browser encounters max="", it expects a valid floating-point number as defined by the HTML specification. An empty string cannot be parsed as a number, so the attribute becomes meaningless and triggers a validation error.

This commonly happens when HTML is generated dynamically by a template engine or framework that outputs an empty value for max when no maximum has been configured. It can also occur when a developer adds the attribute as a placeholder intending to fill it in later.

While most browsers will silently ignore an invalid max value, relying on this behavior is problematic for several reasons:

• Standards compliance: The HTML specification requires max to be a valid floating-point number when present.
• Predictable validation: An empty max means no client-side maximum constraint is enforced, which may not be the developer’s intent. Explicitly removing the attribute makes that intention clear.
• Accessibility: Assistive technologies may read the max attribute to communicate input constraints to users. An empty value could lead to confusing or undefined behavior.

This error applies to input types that accept numeric-style max values, including number, range, date, datetime-local, month, week, and time.

How to Fix It

1. Set a valid numeric value: If you need a maximum constraint, provide a proper floating-point number (e.g., max="100" or max="99.5").
2. Remove the attribute: If no maximum is needed, remove the max attribute entirely rather than leaving it empty.
3. Fix dynamic templates: If your HTML is generated from a template, add a conditional check so that max is only rendered when a value is actually available.

Examples

❌ Invalid: Empty max attribute

<label for="quantity">Quantity:</label>
<input type="number" id="quantity" name="quantity" max="">

The empty string "" is not a valid floating-point number, so this triggers the validation error.

✅ Fixed: Providing a valid numeric value

<label for="quantity">Quantity:</label>
<input type="number" id="quantity" name="quantity" max="100">

✅ Fixed: Removing the attribute entirely

<label for="quantity">Quantity:</label>
<input type="number" id="quantity" name="quantity">

If no maximum constraint is needed, simply omit the max attribute.

❌ Invalid: Empty max on a date input

<label for="end-date">End date:</label>
<input type="date" id="end-date" name="end-date" max="">

✅ Fixed: Valid date value for max

<label for="end-date">End date:</label>
<input type="date" id="end-date" name="end-date" max="2025-12-31">

For date-related input types, the max value must be in the appropriate date/time format (e.g., YYYY-MM-DD for type="date").

Fixing dynamic templates

If you’re generating HTML with a templating language, conditionally include the attribute only when a value exists. For example, in a Jinja2-style template:

<input type="number" id="price" name="price"
  {% if max_price %}max="{{ max_price }}"{% endif %}>

This ensures the max attribute is only rendered when max_price has a valid value, avoiding the empty-string problem entirely.