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Table of Contents
How to add required attribute to the input box?
What types of inputs support required?
Some things to note
Common writing methods in practical applications
Home Web Front-end HTML Tutorial How do I use the required attribute to make an input field mandatory?

How do I use the required attribute to make an input field mandatory?

Jun 20, 2025 pm 01:13 PM

The easiest way to set the required input box in an HTML form is to use the required property. The specific methods are: 1. Directly add the required keyword to the <input> tag to achieve required verification; 2. Supported input types include text, email, password, number, tel, url, checkbox (need to check) and radio (select at least one); 3. It can be used in conjunction with other attributes such as placeholder and pattern to improve user experience; 4. It is necessary to note that it cannot prevent JavaScript from manually calling the checkValidity() method when submitting; 5. It is recommended to combine back-end verification to ensure data security. For example: <input type="text" name="username" required> will force the user to fill in this field before submitting.

In HTML forms, if you want an input box to be filled in before submitting, the easiest way is to use required property. It is a Boolean property. As long as you add it, the browser will automatically help you verify whether this field is empty.


How to add required attribute to the input box?

The usage is very simple, you just need to add the keyword required to the <input> tag. for example:

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

In this way, if the user does not fill in the content in this input box when submitting the form, the browser will prompt them to fill in the content. The prompt styles of different browsers may be slightly different, but a short prompt message will basically pop up.

You can also use it with other attributes, such as placeholder or pattern to enhance user experience and verification logic.


What types of inputs support required?

Not all types of inputs are suitable for adding required restrictions. Common support types include:

  • text
  • email
  • password
  • number
  • tel
  • url
  • checkbox (requires checkbox)
  • radio (select at least one)

For example:

 <input type="email" name="email" required placeholder="Please enter your email">

For check boxes or radio buttons, if required is added, the user must select or check.


Some things to note

Although required is convenient, there are some details that are easily overlooked:

  • JavaScript submission cannot be blocked : If you submit a form manually through JS, such as using form.submit() , the browser will not trigger the default verification behavior. At this time, you need to manually call checkValidity() method.

  • Mobile experience optimization : Sometimes users do not enter smoothly on their phones. It is recommended to combine placeholder and appropriate type (such as email and tel ) to pop up a more suitable keyboard to improve filling efficiency.

  • Don't rely solely on front-end verification : required is a client-side verification method, but it can be bypassed. Therefore, corresponding inspections must be done on the backend to ensure data integrity and security.


Common writing methods in practical applications

A complete form example might look like this:

 

In this way, users must fill in these three items before submitting, and at least 6 characters must be entered in the password.


Basically that's it. Using required can greatly reduce the workload of form verification, but don’t forget to use it with other verification methods to better effect.

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