API Marketplaces. Developer Portals and API Management/API Gateway

API Landscape and API Marketplaces

Rapid API: Find and Connect to Thousands of APIs. RapidAPI is the world's largest API Marketplace, is used by over one million developers to find, test, and connect to thousands of APIs — all with a single account, API Key, and SDK.
dzone: RapidAPI Provides API Marketplace and Insight APIs are driving businesses and innovation.

moesif.com: How to choose the right API Gateway for your platform: Comparison of Kong, Tyk, Apigee, and alternatives
Google Apigee API Manager Apigee is an API management platform for developing, analyzing, securing & scaling various APIs and apps. It provides API technology and services for a wide range of organizations and developers to stimulate the pace of digital business. Through API, Apigee assists businesses to securely share data and services across various channels/devices in order to enhance the customer experience. Companies can manage growth and spikes in API traffic with features like traffic isolation and independent scaling.
- Apigee @Youtube
3scale API Manager
- Red Hat 3scale API Management
- Red Hat 3Scale API Management @Youtube
WSO2 API Manager
- WSO2 @Youtube
Kong API Manager
- Kong API Platform @Youtube
Tyk API Manager
- Tyk @Youtube
Axway API Management
- Axway API Management @Youtube
- axway.com/digitize
MuleSoft API Manager
- MuleSoft @Youtube
Backstage Developer Portal: Spotify has now open-sourced Backstage (under Apache-2.0), the platform of platforms to create a great developer experience across hundreds of squads at Spotify
- Backstage @Youtube