M365 Developer Program

Khushi Shaikh, 

You can use the work tenant credentials for SPFx development. There is no additional licenses required for SPFx development.

But, if you want to have your own personal office 365 developer tenant where you can learn and try anything you want then you can Join the Microsoft 365 Developer Program.

Also, this is a great resource to start with SPFx development: Overview of the SharePoint Framework 

Additional Reference: GitHub - SPFx Samples - You can refer the SPFx samples and learn how community experts are using it. If any sample fulfills your requirement then you can download it from here and use it in your projects (or you can enhance the functionalities as per your requirements after downloading the code ).

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