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.
You could potentially use the redirect option in Constant Contact’s pre-built Lead Generation Landing Page which allows you to add content to your Thank You page, which includes a button link where you can specify the address it will redirect to, but they would have to actually click the button and are not automatically redirected:
Create a Lead Generation Landing Page to collect new contacts
Otherwise, if you are instead looking to build/develop your own website form that redirects to your video sales letter (VSL) automatically after submission, you can program it to connect with our API and sync contacts over automatically by using our Sign-Up Form Endpoint, which allows you to add contacts to an account without having to make a separate API call to check if the email address already exists for a contact in the user account.
Constant Contact provides developers with free access to our V3 API endpoints for developers building their own application for integration. You can get started using our API by visiting our documentation here:
Additionally, you can utilize our API Reference Page to find body schemas & values, as well as test the functionality of our available endpoints to see how they will work once programmed within your application:
Create or Update a Contact Using a Single Method (less recommended)
While our expertise is with our API itself as opposed to its implementation within any particular programming language, we are happy to answer any questions pertaining to Constant Contact’s API endpoints, functionality, and documentation.
**For help with settings or forms within the Constant Contact Website UI (such as setting up a Lead Generation Landing Page) , please reach out to our Support Team at 866-289-2101.
**For further assistance regarding building/developing a form/integration using Constant Contact’s API, please feel free to respond directly to this post, or you can email us directly at firstname.lastname@example.org
Please have a look and let us know if you have any other questions!