Upgrade Guide

The items on this page represent API Implementations that are supported but no longer actively maintained or enhanced. For newer alternatives, please see below.

Using our current API guarantees that you will always have:

  • The latest features

  • Continual updates and improvements

  • The most active community of fellow developers

For questions about migrating an existing solution, please contact our developer support team.



Advanced Integration Method (AIM)

STATUS: Supported

ALTERNATIVE SOLUTIONS: Please refer to the API Reference

DESCRIPTION: Our AIM API has provided a secure, robust and reliable integration for many years. We continue to support the AIM API, but we encourage developers to use our Authorize.Net API, which provides a consistent programming interface across all our feature set (AIM only supports payment transactions).

If you still need to reference AIM NVP documentation, please see the following guides:


PayPal AIM NVP Guide (PDF)   


Server Integration Method (SIM)


ALTERNATIVE SOLUTIONS:SIM is now referred to as Payment Form.

DESCRIPTION: Our hosted payment form and Direct Post Method (DPM) still use our SIM API. You can find everything you need to know about integrating with those features in our Server Integration Method (SIM) Guide (PDF).