magento 2 remove main menu

Add the below code in your theme’s default.xml file

<?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>
        <referenceBlock name="navigation.sections" remove="true"/>
    </body>
</page>

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