WordPress.com REST API Developer Console - superceded by https://github.com/Automattic/rest-api-console2
An open source version of https://developer.wordpress.com/docs/api/console/ that you can run yourself. Uses implicit OAuth for authentication. The console requires a WordPress.com application to be created.
Once you have your application credentials you need to create a configuration file for your application.
Wherever you have placed the console (the index.html, js, and css folders) create a "config.json" file with the following contents:
{
"client_id": _CLIENT_ID_,
"redirect_uri": "_REDIRECT_URI_"
}
You can use the config.sample.json as a base.
Replace _CLIENT_ID with the ID from above and REDIRECT_URI with the URI from above.
You should now be able to load the console and authenticate using the box in the lower right hand corner.