You can now configure custom domains for your APIs on Amazon API Gateway using SSL/TLS certificates provisioned and managed by AWS Certificate Manager (ACM). Now, you can request a certificate from ACM and associate it with your API in minutes using the API Gateway Console, APIs, and CLI/SDKs. Previously, you needed to procure and upload your own SSL certificates to API Gateway in order to configure a custom domain for your APIs.
AWS Certificate Manager is a service that lets you easily provision, manage, and deploy Secure Sockets Layer/Transport Layer Security (SSL/TLS) certificates for use with AWS services. AWS Certificate Manager removes the time-consuming manual process of purchasing, uploading, and renewing SSL/TLS certificates. SSL/TLS certificates provisioned through AWS Certificate Manager are free. You pay only for the AWS resources you create to run your application.