# Pay API ThirdFi offers Fiat-to-Crypto (On-ramp) payment services with REST API. ThirdFi allows developer apps to enable users to buy crypto directly inside their apps using fiat currencies via different payment methods such as cards, bank transfers, and other local payment methods. ThirdFi integrated with [Transak](https://transak.com/) to provide enhanced on-ramp services with Transak Widget UI, which can be **integrated into the developer server backend** via REST API. Transak also helps us to verify the user KYC during the on-ramp payment services. In the future, there will be more payment solution providers to be integrated in ThirdFi API. ### How to use this Fiat-to-crypto On-ramp API? 1. Sign up for the ThirdFi app. 2. Log in, and generate the API key. 3. Create customers through the Customer API. 4. Use the customer email address to create the payment request via Payment API, and redirect the user to the payment webview. 5. Users can do the transaction by connecting web3 wallet and confirming the transaction. 6. ThirdFi sends the webhook event to the developer's backend server after configuring the webhook setting. Visit here to try the Pay API for free! {% embed url="" %} --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://thirdfi.gitbook.io/thirdfi.org/product/pay-api.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.