To set required fields in HTML forms, 1. Use the required attribute to achieve it; 2. This attribute is Boolean, no value is required, and is suitable for common input types such as text, email, password, etc.; 3. The browser will automatically verify when submitting, and if it is not filled in, it will be blocked and prompted; 4. The prompt information is not customized by default, and can be adjusted through the JavaScript setCustomValidity() method; 5. Note that you cannot rely solely on front-end verification, the back-end still needs to verify data; 6. The performance of the mobile side may be inconsistent, and it is recommended to test the target platform; 7. Avoid multiple required fields simultaneously reporting errors that affect the user experience.
In HTML forms, if you want an input field to be required, the easiest and most effective way is to add required
attribute to the input
tag. In this way, the browser will automatically check when the user submits the form. If the field is empty, the user will be prompted to fill in it.

Here are some practical questions and suggestions that you may be concerned about when using this property.
How to use required
attribute correctly
To make an input box a required item, you only need to add the required
Boolean property to the tag, and there is no need to assign values. For example:

<input type="text" name="username" required>
Or use it with other types, such as email, password, etc.:
<input type="email" name="email" required>
As long as this attribute is added, the user will not be able to submit the form if it is not filled in, and the browser will automatically pop up the prompt message. The prompts displayed by different browsers may be different, but they will generally focus on unfilled fields.

What types of inputs support required?
Not all input
types are suitable for use with required
, but most common ones are supported. Here are some commonly used and well-compatible combinations:
-
text
-
email
-
password
-
number
-
checkbox
-
radio
-
select
(drop-down selection) -
file
For example, after the check box is added with required
, the user must check it before submitting; while the radio button group needs to be selected at least one of the verifications.
It should be noted that although hidden
types also support required
, they are easily ignored because they cannot be seen by users, so be especially careful when using them.
Some common things to note
Although required
looks simple, there are still several error-prone places in actual development:
Don't rely solely on front-end verification :
required
is a browser-side verification mechanism and cannot replace back-end data verification. Malicious users can bypass front-end restrictions by disabling JS or sending requests directly.Prompt information is not customizable (by default) : The prompts that come with the browser are usually more basic. If you want to customize the prompt content, you can use
setCustomValidity()
method in combination with JavaScript.Note for mobile experience : some browsers on mobile devices do not handle
required
in a consistent manner. It is best to test the performance of the main target platform.Avoid reporting too many errors from multiple empty fields at the same time : If a form has many
required
fields, users may see many prompts at once when submitting, and the experience is not very good. At this time, you can use JavaScript to control only one error at a time, or remind it in order.
Basically that's it. Use required
reasonably can greatly improve the usability and data quality of forms, but you should also note that it is just the first layer of defense for verification.
The above is the detailed content of HTML `input` `required` Attribute for Mandatory Fields. For more information, please follow other related articles on the PHP Chinese website!

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