How do I create a Square developer account?
Square developer accounts are the same as Square merchant accounts. If you already have a Square account, you're all set.
If you don't already have a Square account, create one to start using the API. Most API calls can be made without activating payment processing.
If you're planning to use Square APIs to create card payments, be sure to activate after you create your account to ensure your account is enabled for payment processing. For instance if you are testing production eCommerce or Point of Sale API transactions in your developer account, you will want to do this.
After you create your Square account, see Square APIs: Getting Started to learn the basics of using Square APIs.