Captions are not baked into your video file. Think of Gratavid captions as a layer above your video. Layered captions, also referred to as video tracks, are a web standard for adding captions to a video. The video track's primary benefit is to ensure ADA compliance. Screen readers for blind or visually impaired users can read video tracks, but they can't read captions that are baked into the video.
Technically speaking, video tracks are created using a WEBVTT file. When you generate captions in Gratavid, we automatically create a WEBVTT file and sync it with your video.
For more technical information on video captions and WEBVTT files, visit adding captions and subtitles to HTML5 video.