An Azure service that provides a hybrid, multi-cloud management platform for APIs.
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As stated in Access to product APIs
The open products aren't listed in the developer portal for developers to learn about or subscribe to. They're visible only to the Administrators group. You'll need to use another mechanism to inform developers about APIs that can be accessed without a subscription key.
Open products have the Requires subscription setting disabled, which means that users don't need to subscribe to them. For this reason, open products don't appear on the Products page of the developer portal, refer Enable or disable subscription requirement for API or product access for more details.
Alternatively:
Developers can access an open product's APIs without a subscription key. However, you can configure other mechanisms to secure client access to the APIs, including OAuth 2.0, client certificates, and restricting caller IP addresses.
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