Bad value “” for attribute “min” on element “input”: The empty string is not a valid floating point number.

The min attribute defines the minimum acceptable value for form input types such as number, range, date, time, datetime-local, week, and month. When the browser or the W3C validator encounters min="", it attempts to parse the empty string as a floating point number and fails because the empty string is not a valid representation of any number according to the HTML specification’s rules for parsing floating point numbers.

This issue commonly arises when templating engines or server-side code dynamically set the min attribute but output an empty value when no minimum is configured, or when developers add the attribute as a placeholder intending to fill it in later.

Why this matters

• Standards compliance: The HTML specification explicitly requires the min attribute’s value to be a valid floating point number (for numeric types) or a valid date/time string (for date/time types). An empty string satisfies neither requirement.
• Unpredictable browser behavior: When browsers encounter an invalid min value, they typically ignore the attribute entirely. This means your intended constraint silently disappears, potentially allowing users to submit out-of-range values.
• Accessibility concerns: Assistive technologies may rely on min and max to communicate valid input ranges to users. An invalid value can lead to confusing or missing guidance for screen reader users.
• Form validation issues: Built-in browser validation using the Constraint Validation API depends on valid min values. An empty string can cause the browser’s native validation to behave inconsistently across different browsers.

How to fix it

You have two straightforward options:

1. Provide a valid value: Set min to the actual minimum number or date/time string you want to enforce.
2. Remove the attribute: If no minimum constraint is needed, simply omit the min attribute. The input will then accept any value within its type’s natural range.

If your min value comes from dynamic server-side or JavaScript logic, make sure the attribute is only rendered when a valid value is available, rather than outputting an empty string as a fallback.

Examples

❌ Invalid: empty string for min

<input type="number" min="" max="10">

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

✅ Fixed: provide a valid number

<input type="number" min="0" max="10">

✅ Fixed: remove min if no minimum is needed

<input type="number" max="10">

❌ Invalid: empty min on a range input

<input type="range" min="" max="100" step="5">

✅ Fixed: valid min on a range input

<input type="range" min="0" max="100" step="5">

❌ Invalid: empty min on a date input

<input type="date" min="" max="2025-12-31">

For date inputs, min must be a valid date string in YYYY-MM-DD format — an empty string is equally invalid here.

✅ Fixed: valid min on a date input

<input type="date" min="2025-01-01" max="2025-12-31">

Handling dynamic values in templates

If you’re using a templating language and the minimum value might not always exist, conditionally render the attribute rather than outputting an empty value. For example, in a generic template pseudocode:

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

<input type="number" min="" max="10">

<!-- Only include it when a value is available: -->

<input type="number" min="5" max="10">

In practice, use your templating engine’s conditional logic (e.g., {% if min_value %}min="{{ min_value }}"{% endif %} in Jinja2, or similar constructs) to ensure min is only present when it holds a valid value.

Learn more:

MDN Reference

MDN: HTML attribute min

→

MDN Reference

MDN: input: min

→

WHATWG Spec

WHATWG HTML Living Standard: the input element

→