HTML Guides for maxlength

The maxlength attribute provides built-in client-side validation that caps the number of characters a user can type into a field. Browsers enforce this by preventing further input once the limit is reached. However, this behavior only makes sense for input types that accept arbitrary text strings. Input types like number, date, range, and checkbox have their own value formats and constraints — a number input’s value is controlled by min, max, and step, not by character count.

When you place maxlength on an unsupported input type, browsers will ignore the attribute. This means it provides no actual validation while giving a false sense of security. It also produces invalid HTML, which can cause issues with assistive technologies that may try to interpret the attribute and relay incorrect information to users. Keeping your markup valid ensures predictable behavior across browsers and a better experience for all users.

How to fix it

1. Remove maxlength from any <input> whose type is not email, password, search, tel, text, or url.
2. Use the correct constraint attributes for the input type in question. For number inputs, use min and max. For date inputs, use min and max with date strings.
3. If you genuinely need character-length validation, consider whether a text-based input type is more appropriate for your use case, or implement the constraint in JavaScript.

Examples

❌ Invalid: maxlength on a number input

<label for="quantity">Quantity</label>
<input type="number" id="quantity" name="quantity" maxlength="3">

The number type does not support maxlength. Browsers will ignore it, and the HTML is invalid.

✅ Fixed: using min and max for a number input

<label for="quantity">Quantity</label>
<input type="number" id="quantity" name="quantity" min="0" max="999">

If the goal was to limit the value to three digits, min and max are the correct constraints.

❌ Invalid: maxlength on a date input

<label for="start-date">Start date</label>
<input type="date" id="start-date" name="start-date" maxlength="10">

Date inputs have a browser-provided date picker, and their values are always in YYYY-MM-DD format. The maxlength attribute has no effect here.

✅ Fixed: using min and max for a date input

<label for="start-date">Start date</label>
<input type="date" id="start-date" name="start-date" min="2020-01-01" max="2030-12-31">

❌ Invalid: maxlength on a checkbox

<label>
  <input type="checkbox" name="agree" maxlength="1"> I agree
</label>

A checkbox is a boolean toggle — character length is meaningless here.

✅ Fixed: removing the invalid attribute

<label>
  <input type="checkbox" name="agree"> I agree
</label>

✅ Valid: maxlength on supported text-based types

<label for="username">Username</label>
<input type="text" id="username" name="username" maxlength="30">

<label for="user-email">Email</label>
<input type="email" id="user-email" name="email" maxlength="254">

<label for="user-phone">Phone</label>
<input type="tel" id="user-phone" name="phone" maxlength="15">

<label for="site-url">Website</label>
<input type="url" id="site-url" name="website" maxlength="2048">

<label for="user-pass">Password</label>
<input type="password" id="user-pass" name="password" maxlength="128">

<label for="query">Search</label>
<input type="search" id="query" name="q" maxlength="100">

All six of these input types support maxlength because they accept free-form text where limiting character count is meaningful.

Remove the empty maxlength value and provide a non-negative integer or omit the attribute entirely.

Explanation

The maxlength attribute on an input element must be a valid non-negative integer per the HTML specification. An empty string ("") is invalid and triggers the validator error.

• Valid: a decimal integer like 0, 10, 255.
• Invalid: empty string, negative numbers, non-numeric strings, or whitespace.
  If no maximum length is needed, omit maxlength instead of leaving it empty.
  Note that maxlength applies to text-entry controls such as type="text", search, url, tel, email, and password. For other types (e.g., number, date), maxlength is ignored and should not be used.

Examples

Correct: set an explicit maximum

<input type="text" name="username" maxlength="20">

Correct: no maximum, omit the attribute

<input type="text" name="comment">

Incorrect: empty string (validator error)

<input type="text" name="username" maxlength="">

Remove the empty maxlength and provide a valid non‑negative integer, or omit maxlength entirely.

The maxlength attribute limits the number of characters a user can enter. It must be a valid non-negative integer (0, 1, 2, …). An empty string, whitespace, or non-numeric value fails validation. When maxlength is omitted, the length is unlimited. When set to 0, no characters can be entered. The value applies to the textarea element itself, not its content.

Common fixes:

• Set maxlength to a concrete number like 200.
• If you don’t need a limit, remove the attribute.
• Ensure templating doesn’t output an empty attribute (e.g., maxlength="").

HTML Examples

Invalid example (reproduces the validator error)

<!DOCTYPE html>
<html lang="en">
<head>
  <title>Invalid maxlength</title>
</head>
<body>
  <form>
    <label for="msg">Message</label>
    <textarea id="msg" name="message" maxlength=""></textarea>
  </form>
</body>
</html>

Fixed example (valid integer or omit attribute)

<!DOCTYPE html>
<html lang="en">
<head>
  <title>Valid maxlength</title>
</head>
<body>
  <form>
    <label for="msg">Message (max 200 chars)</label>
    <textarea id="msg" name="message" maxlength="200"></textarea>
  </form>
</body>
</html>

When you write an attribute like maxlength="200 and accidentally omit the closing quote, everything that follows — including subsequent attribute names and their values — gets absorbed into that one attribute’s value. In this case, the validator sees the value of maxlength as 200 aria-required= (or similar), which is not a valid integer. The parser doesn’t encounter a closing " until it finds the next quotation mark further along in the tag, causing a cascade of errors.

This is a problem for several reasons:

• Broken functionality: The maxlength attribute won’t work because 200 aria-required= is not a valid number. The browser cannot determine the intended character limit.
• Lost attributes: The aria-required attribute is swallowed into the malformed maxlength value, so it never gets applied as a separate attribute. Assistive technologies like screen readers won’t know the field is required.
• Accessibility impact: Since aria-required="true" is lost, users who rely on screen readers won’t receive the information that the field is mandatory, potentially leading to form submission errors and a frustrating experience.

The root cause is almost always a missing closing quotation mark. Carefully check that every attribute value has both an opening and a closing ". This kind of typo is easy to make and easy to miss, especially in long tags with many attributes.

Examples

Incorrect — missing closing quote on maxlength

The closing " after 200 is missing, so the value of maxlength extends all the way to the next quotation mark it finds:

<input type="text" name="nome" id="nome" maxlength="200 aria-required="true">

The validator interprets maxlength as having the value 200 aria-required=, and only true ends up as the value of an unintended or malformed attribute. Nothing works as expected.

Correct — properly quoted attributes

Each attribute has its own properly matched pair of quotation marks:

<input type="text" name="nome" id="nome" maxlength="200" aria-required="true">

Here, maxlength="200" correctly limits the input to 200 characters, and aria-required="true" is a separate attribute that tells assistive technologies the field is required.

Incorrect — missing closing quote with more attributes

This issue can happen with any combination of attributes. Here, a missing quote after maxlength absorbs class and placeholder:

<input type="text" maxlength="50 class="username" placeholder="Enter name">

Correct — all quotes properly closed

<input type="text" maxlength="50" class="username" placeholder="Enter name">

Tips for avoiding this issue

• Use a code editor with syntax highlighting. Most editors color attribute values differently from attribute names. If you see an attribute name rendered in the same color as a value string, a quote is likely missing.
• Format attributes one per line on complex elements. This makes it much easier to spot mismatched quotes:

<input
  type="text"
  name="nome"
  id="nome"
  maxlength="200"
  aria-required="true">

• Validate early and often. Running your HTML through the W3C validator regularly helps catch these small typos before they cause confusing bugs in production.