I had a checkbox in a React component:

<input name="enable" type="checkbox" />

and I wanted it to be checked by default, yet the user could change its value.

Using

<input name="enable" type="checkbox" checked="checked" />

didn’t work. The checkbox state could not be changed.

The solution was to use the defaultChecked attribute:

<input name="enable" type="checkbox" defaultChecked={true} />

If the checkbox needs to be checked depending if the value was checked in a variable (for example in an editing form when you are getting the actual value from the database) you can use

<input name="enable" type="checkbox" defaultChecked={existing_enable_value} />