The Timed Text Working Group published IMSC Text Profile 1.3 as a W3C Recommendation.

IMSC Text Profile 1.3 is the most recent addition to the IMSC family of specifications for the authoring and delivery of subtitles and captions worldwide. The rich styling and structured markup make it an ideal choice for expressive subtitles and AI training sets.
https://www.w3.org/news/2026/imsc-text-profile-1-3-is-now-a-w3c-recommendation/
#WebStandards #TimedText #Subtitles #StructuredMarkup