Upfile-builder is a package from the Upfile project which allows the services to upload files into the BSV blockchain. The Upfile-builder creates the required outputs for the transaction(s) and passes them to a handler. The handler is responsible for making the payment, broadcasting the transaction(s), and returning the transaction ID. This ID is the key to finding all the transactions. Below is an example that uses the upfile-builder with Handcash connect as a handler.