In this blog, we will learn what SharePoint Framework (SPFx) extensions are and what its different types are. We know that SharePoint Framework is a page part model. SPFx is a modern web-based development that is built on modern technologies, node-based development, SCSS, Typescript and we can use any JavaScript framework like React or Angular.
We know we can create web parts using SharePoint Framework. We can also change basic layout of header or footer using SPFx extensions.
Types of SPFx extensions
We can create 3 types of SPFx extensions.
- Application Customizers
- Field Customizers
- CommandSets
Application Customizers allow you to change fixed areas on a page or inject logic using JavaScript. Application Customizers provide access to well-known locations on SharePoint pages that you can modify based on your business and functional requirements.
Field Customizers allow you to control the rendering of any field in a SharePoint List.
CommandSets allow you to put custom commands in the toolbar.
SharePoint Education 
Good Article. Got to know about SPFx extensions.
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