Twelve-Factor App methodology

The Twelve-Factor App methodology is a methodology for building software-as-a-service applications. These best practices are designed to enable applications to be built with portability and resilience when deployed to the web.
History.
The methodology was drafted by developers at Heroku, a platform-as-a-service company, and was first presented by Adam Wiggins circa 2011.
Criticism and adaptation.
A number of commentators have argued that the relevance of the Twelve-Factor app concept is limited to Heroku. The twelve factors are however cited as a baseline from which to adapt or extend.