Optional idAn optional ID.
The line defines positioning of the cue box.
An alignment for the cue box’s line.
The position defines the indent of the cue box in the direction defined by the writing direction.
An alignment for the cue box in the dimension of the writing direction.
https://www.w3.org/TR/webvtt1/#webvtt-cue-position-alignment
Optional regionAn optional WebVTT region to which a cue belongs.
A number giving the size of the cue box, to be interpreted as a percentage of the video, as defined by the writing direction.
A boolean indicating whether the line is an integer number of lines, or whether it is a percentage of the dimension of the video.
https://www.w3.org/TR/webvtt1/#webvtt-cue-snap-to-lines-flag
Writing direction.
An alignment for all lines of text within the cue box, in the dimension of the writing direction.
https://w3.org/TR/webvtt1/#webvtt-cue-text-alignment