Use subtitles and closed captions
You can customize the display of subtitles and captions, and choose to use subtitles for the deaf and hard of hearing (SDH) or closed captions, whenever they’re available.
Choose Apple menu > System Preferences, click Accessibility, then click Captions.
Do any of the following:
Enable closed captions and SDH: Select the “Prefer closed captions and SDH” checkbox.
Stop using closed captions and SDH: Deselect the “Prefer closed captions and SDH” checkbox.
Create a style: Click the Add button
, enter a name for the style, then change settings for the background and text. To have your style setting always used, deselect the “Allow video to override” checkbox.Edit a style you created: Select the style in the list, then click Edit.
Delete a style you created: Select the style in the list, then click the Remove button
.