Hello JasonM15890,   Thank you for reaching out to Constant Contact API Developer Support. My team is here to assist outside software developers with questions about building into Constant Contact's API.   The request for V3 application code samples is currently under review. However, we're currently still adding endpoints and capabilities to the V3 API, and do not plan to publish official sample apps until that process is complete. Your feedback and experience with this request is essential to improving our product, so thank you for reaching out to us regarding this matter.   For updates on which new features and endpoints have been released for Constant Contact's V3 API, you can stay updated by checking the Constant Contact V3 API Release Notes page:   V3 API - Release Notes https://developer.constantcontact.com/api_guide/index.html   In the meantime, here are the example calls that are currently available for V3:   V3 Code Samples: https://v3.developer.constantcontact.com/api_guide/tag_code_samples.html    Additionally, you can utilize our API Reference tester to test out the functionality of our available endpoints to see how they will work once programmed within your application: https://v3.developer.constantcontact.com/api_reference/index.html   The Client Secret is used to authorize requests made to the authorization server. You can obtain your application’s client secret in the Developer portal with the following steps:   Login to your account at https://app.constantcontact.com/pages/dma/portal/ Select the name of your V3 API key Select the blue “Generate Client Secret” button under the “App Details” section of the “Details” tab.   Please have a look and let us know if you have any other questions!   Regards, ... View more