API previews let you try out new APIs and changes to existing API methods before they become part of the official GitHub API.
During the preview period, we may change some features based on developer feedback. If we do make changes, we'll announce them on the developer blog without advance notice.
To access an API preview, you'll need to provide a custom media type in the Accept header for your requests. Feature documentation for each preview specifies which custom media type to provide.
Content attachments
You can now provide more information in GitHub for URLs that link to registered domains by using the Content Attachments API. See "Using content attachments" for more details.
Custom media types: corsair-preview
Announced: 2018-12-10