how to make an input tag unchangable code example

Example 1: read only attribute in html

<!-- Using readonly attribute is use to prevent changing of input value. -->
Example:
<input type="text" name="username" value="ankur" readonly>

Example 2: read only html

<!-- Using readonly attribute is use to prevent changing of input value. -->
Example:
<input type="text" name="username" value="lol" readonly>