Transloadit

What are Captions?

Captions are time-aligned text tracks that convey spoken dialogue along with speaker identity and meaningful non-speech sounds a viewer needs to follow the content. They can be embedded in media or delivered as a separate selectable resource.

How Captions work

A caption file or stream is organized into cues containing timing, text, and sometimes positioning or style instructions. Unlike a transcript, it participates in the playback timeline; unlike dialogue-only subtitles, captioning conveys speakers, music, and meaningful non-speech audio, which is what qualifies a track for accessibility use. Authoring occurs after transcription or translation, followed by timing review, format conversion, packaging, and player validation across the intended languages and devices.

Key facts

  1. WebVTT is widely used for web text tracks, while TTML-family documents are common in professional exchange and streaming; conversion can lose styling or placement not shared by both models.
  2. Overlapping cues, line wrapping, and safe-area placement must be tested against real video because syntactically valid captions can still obscure important graphics or one another.
  3. Burned-in captions become image pixels and work without track support, but viewers cannot disable them, search them as text, or independently select another caption language.

When Captions matter

Add captions to support accessibility, silent viewing, localization, indexing, and search. Incorrect timing or character encoding can make an otherwise valid track difficult or impossible to follow.

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