Hi @ca136
Our server-side APIs are set up to deny incoming connections from the front-end in order to prevent people from exposing their sensitive private API keys which are required for these endpoints. When sending subscriptions to Klaviyo, here are our recommended approaches:
- If you want to use an API endpoint, use the server-side subscribe endpoint from a server-side location
- If you do not have access to a server-side location for your platform (eg. you’re on a hosted platform), you can set up a proxy which routes a request to subscribe from your front-end to this proxy in order to send the server-side request
- Alternatively, an easy way to set up subscribes from the front-end would be to use our built-in forms or one of our partner integrations who offer subscription forms
Hope that information helps but if you need additional information, please do follow up.