Here I will explain how to add attributes to the body tag. Magento 2 by default adds the controller name and the page layout name as class to the body tag. In this blog I will explain how you can add your own class to the body tag and also I’ll add an attribute with its value.
In the layout file add the following,
<?xml version="1.0"?>
<page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
<body>
<attribute name="class" value="custom-class"/>
<attribute name="data-var" value="some-data"/>
</body>
</page>
The attribute tag is use add attributes to the body.