> For the complete documentation index, see [llms.txt](https://docs.galaxypay.vn/upc/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.galaxypay.vn/upc/payment-gateway/api-specification.md).

# API Specification

- [Integration Keys](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/integration-keys.md)
- [Definitions](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/definitions.md)
- [Message Structure](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/definitions/message-structure.md)
- [Signature Algorithm](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/definitions/signature-algorithm.md)
- [Data Flight](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/data-flight.md): Apply only for VJ
- [PAYMENT](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/payment.md)
- [Pay](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/payment/pay.md): Use to create a simple payment request. Use for Merchant checkout and Merchant Hosted checkout.
- [Pay with create token](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/payment/pay-with-create-token.md)
- [Pay with token](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/payment/pay-with-token.md)
- [Pay with Option](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/payment/pay-with-option.md): Use to create a payment request with payment options, then customer can select the payment methods at GALAXY PAY
- [Pay with QR](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/payment/pay-with-qr.md): Use to create a dynamic QR payment request, then customer can scan the QR code and process the payment on any banking mobile applications.
- [Checkout(for modal checkout)](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/payment/checkout-for-modal-checkout.md): Use to create a simple pre-order payment request
- [Payment Link](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/payment/payment-link.md): Use to create a dynamic payment link.
- [Fast pay](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/payment/fast-pay.md)
- [TOKENIZATION](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/tokenization.md)
- [Merchants](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/tokenization/merchants.md)
- [Create Token](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/tokenization/merchants/create-token.md): Use to create a card token. Only apply for Merchant using fast pay solution.
- [Delete Token](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/tokenization/merchants/delete-token.md): Use to delete the existing tokens. Only apply for Merchant administration page.
- [Customers](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/tokenization/customers.md)
- [Query Tokens](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/tokenization/customers/query-tokens.md): Use to get the list of card tokens for the specified customer.
- [Remove Token](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/tokenization/customers/remove-token.md): Use to remove a existing card token for the specified customer.
- [MANAGEMENT](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/management.md)
- [Query Transaction](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/management/query-transaction.md): Use to query a transaction status.
- [Refund Transaction](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/management/refund-transaction.md): Use to refund a successful transaction.
- [Void Transaction](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/management/void-transaction.md): Use to void a successful transaction.
- [Capture Transaction](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/management/capture-transaction.md): Use to capture a successful transaction.
- [IPN & CALLBACK](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/ipn-and-callback.md)
- [Result & IPN Callback](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/ipn-and-callback/result-and-ipn-callback.md)
- [Cancel Callback](https://docs.galaxypay.vn/upc/payment-gateway/api-specification/ipn-and-callback/cancel-callback.md)