Guideline A.2.1: (For the authoring tool user interface) Make alternative content available to authors. [Implementing A.2.1] http://www.w3.org/TR/2015/NOTE-IMPLEMENTING-ATAG20-20150924/#gl_a21 Rationale: Some authors require access to alternative content in order to interact with the web content that they are editing. A.2.1.1 Text Alternatives for Rendered Non-Text Content: If an editing-view renders non-text content, then any programmatically associated text alternatives for the non-text content can be programmatically determined. (Level A) Implementing A.2.1.1 http://www.w3.org/TR/2015/NOTE-IMPLEMENTING-ATAG20-20150924/#sc_a211 A.2.1.2 Alternatives for Rendered Time-Based Media: If an editing-view renders time-based media, then at least one of the following is true: (Level A) (a) Option to Render: The authoring tool provides the option to render alternatives for the time-based media; or (b) User Agent Option: Authors have the option to preview the time-based media in a user agent that is able to render the alternatives. Implementing A.2.1.2 http://www.w3.org/TR/2015/NOTE-IMPLEMENTING-ATAG20-20150924/#sc_a212