Public Preview generates a preview link for all posts that have the public-preview post type support (post automatically inherits this privilege). The link is unique to the post and has measures to prevent direct access by link guessing.
Usage
Simply add ‘public-preview’ to your ‘supports’ array when registering your post type. Once you’ve done this, a ‘Preview Link’ will appear on the relevant posts when in a draft state. This link can be shared to show previews.
v1) Initial version launched from a previously private plugin