The Plex Node.js Library by Phillip Johnsen allows developers to integrate the Plex API into their Node.js applications. Usage examples are included in the documentation.
Microsoft announced availability of the ORTC API preview for Edge. ORTC API support is not yet available in other browsers which may pose some difficulties for app developers.
In January 2019, Google is deprecating its Picasa Web Albums Data API and disabling all associated OAuth scopes. Any existing applications using the API will continue to work until that time. In March 2019, the Picasa Web Albums API will be turned off at which point all calls will fail.