HTML Checking for Large Sites

The maxlength attribute can be used on an input element to define a client-side validation for the maximum length allowed on an input without resorting to JavaScript.

This attribute is only allowed on elements of type email, password, search, tel, text, or url.

The minlength attribute can be used on an input element to define a client-side validation for the maximum length allowed on an input without resorting to JavaScript.

This attribute is only allowed on elements of type email, password, search, tel, text, or url.

The minlength attribute defines the minimum number of characters (as UTF-16 code units) the user can enter into an <input> or <textarea>. This must be an integer value 0 or higher. If no minlength is specified, or an invalid value is specified, the input has no minimum length. This value must be less than or equal to the value of maxlength, otherwise the value will never be valid, as it is impossible to meet both criteria.

Here’s an example:

<label for="name">Enter your name (max 25 characters)</label>
<input type="text" minlength="25" id="name">

The pattern attribute is only allowed on input whose type is email, password, search, tel, text or url. Check the type used, and consider changing to one of the allowed types to enable pattern client-side validation.

The pattern attribute is a handy way of adding client-side validation on HTML forms without resorting to JavaScript. Check out this article to learn more about Input Pattern.

The value tel-national cannot be used on the attribute autocomplete of an <input> element of type tel. Either change to type="text", or use autocomplete="tel". Examples:

<!-- Using autocomplete "tel-national" on type "tel" is invalid -->
<input name="phone1" type="tel" autocomplete="tel-national" />

<!--Using autocomplete "tel-national" on type "text" is valid -->
<input name="phone2" type="text" autocomplete="tel-national" />

<!--Using autocomplete "tel" on type "tel" is valid -->
<input name="phone3" type="tel" autocomplete="tel" />

The aria-required attribute is used to indicate to screen reader users that a form input is required. As there is now in HTML a general required attribute which works with most user agents, it’s unnecessary to use both at the same time. In general, you can rely solely on the required attribute, unless you want to provide backwards compatibility on old screen reader software versions.

Example:

<form action="order.">
  <!-- This will raise a warning on unnecesary attributes -->
  <input id="city" name="city" aria-required="true" required />

  <!-- You can use this instead -->
  <input id="city" name="city" required />
</form>

<input> elements can’t have a search role. Instead, try with <input type="search">.

<input> elements of type search are text fields designed for the user to enter search queries into. These are functionally identical to text inputs, but may be styled differently depending on the user agent.

The search role is a landmark. Landmarks can be used by assistive technology to quickly identify and navigate to large sections of the document. The search role is added to the container element that encompasses the items and objects that, as a whole, combine to create search functionality. When a <form> is a search form, use the search role on the form.

Example of a search form:

<form role="search">
  <label for="search-input">Search this site</label>
  <input type="search" id="search-input" name="search">
  <input value="Submit" type="submit">
</form>

The href attribute on an <a> link contains a space character, which is not allowed. If you’re trying to link to a phone URL, review the href attribute to remove unallowed characters, as in this example:

<!-- Invalid as it contains a space character -->
<a href="tel: +123456789">call me</a>

<!-- Valid -->
<a href="tel:+123456789">call me</a>

The value used in the datetime attribute is not in a valid format.

The <time> HTML element represents a specific period in time. It may include the datetime attribute to translate dates into machine-readable format, allowing for better search engine results or custom features such as reminders.