


How do I use the checked attribute to specify that a checkbox should be checked by default?
Jun 27, 2025 am 01:28 AMTo make the checkbox selected by default in HTML, just add the checked attribute in the <input> tag. The specific syntax is: <input type="checkbox" name="example" checked>, without JavaScript or extra logic; 1. It can be used in scenarios such as preset options for form (such as agreeing to terms), retained status during editing, and multiple choice default items; 2. The writing method can be abbreviated as checked or completely written as checked="checked", but the former is recommended to be more concise; 3. Note that this attribute is a Boolean type, and it takes effect when it exists. When dynamically generating HTML, you need to ensure that its output is correct; 4. Although JavaScript can also be implemented by setting .checked = true, using HTML attributes in static pages is more intuitive and reliable.
In HTML, if you want a checkbox to be selected by default, you only need to add checked
attribute to the corresponding <input>
tag. No additional JavaScript or complex logic is required, pure HTML can do it.
How to use checked
attribute correctly
To make a checkbox checked by default, the syntax is very simple:
<input type="checkbox" name="example" checked>
As long as the checked
property is added, regardless of whether there is a value or not, the browser will think that this checkbox should be selected by default. You can also write it as checked="checked"
, but most of the time, it is more concise to write checked
directly.
Common application scenarios
- Form preset options : For example, in the registration page, the default check "I have read and agreed to the terms of service".
- Status when editing existing data : The option selected by the user before remains checked when the edit page is displayed again.
- Default items in multiple selection scenarios : For example, in the settings interface, some functions are enabled by default.
For example:
<label> <input type="checkbox" name="subscribe" checked> Subscribe to our newsletter</label>
In this way, the check box before "Subscribe to our newsletter" will be checked by default when the page loads.
Notes and FAQs
-
checked
is a Boolean property, which means "true" as long as it exists, and no assignment is required. - If you are dynamically generating HTML (such as using PHP or JavaScript), make sure that the property is indeed output to the tag.
- In JavaScript, you can set the default state by
.checked = true
, but if it is a static page, it is recommended to usechecked
attribute of HTML directly to be more intuitive and reliable.
Basically that's it. The usage is not complicated, but it is easy to ignore whether it really takes effect in development, especially when rendering dynamically.
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