Optional
idAn optional ID.
The line defines positioning of the cue box. https://www.w3.org/TR/webvtt1/#webvtt-cue-line
An alignment for the cue box’s line. https://www.w3.org/TR/webvtt1/#webvtt-cue-line-alignment
The position defines the indent of the cue box in the direction defined by the writing direction. https://www.w3.org/TR/webvtt1/#webvtt-cue-position
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. https://www.w3.org/TR/webvtt1/#webvtt-cue-region
A number giving the size of the cue box, to be interpreted as a percentage of the video, as defined by the writing direction. https://www.w3.org/TR/webvtt1/#webvtt-cue-size
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. https://www.w3.org/TR/webvtt1/#webvtt-cue-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