Captions are time-stamped text renderings of the spoken audio track in a video, displayed synchronously inside or below the player frame so that learners can read what is being said. WCAG 2.1 AA Success Criterion 1.2.2 mandates captions for all pre-recorded synchronised media, making them a legal requirement on most corporate and public-sector learning platforms. Captions differ from subtitles in that they also convey non-speech audio information such as "[alarm sounds]" or "[music]" that is relevant to understanding the content. In practice, captions are generated in two ways: automatically via ASR (Automatic Speech Recognition) engines such as Whisper or vendor APIs, then human-reviewed for accuracy; or produced manually from a transcript. Common delivery formats are WebVTT for web players and SRT for offline or upload workflows; both are plain-text files pairing timecodes with caption text. Beyond accessibility, captions drive measurable engagement: learners watch longer, comprehension improves for non-native speakers, and the text is indexed for in-video search. The main quality risk with auto-generated captions is technical vocabulary errors; a human review step is essential before any captions are considered accessible. Caption styling — font size, contrast, and placement — is itself subject to WCAG colour-contrast requirements.
The handbook · 7 volumes
Fora Soft Video Engineering Handbook
Captions are an accessibility requirement and one of the cheapest ways to raise watch time, as long as they stay in sync. We wrote seven volumes that cover the whole video stack; for captions start with Volume 4, which covers accessibility, subtitles and clear voice, with Volume 6 on ASR and Volume 3 on caption tracks in players. Written by Nikolay Sapunov, CEO at Fora Soft.
Need accurate captions across your whole course library?
Send us sample lectures and we will give you a captioning workflow with ASR choice, review steps, player formats and cost per video hour. 250+ video products shipped since 2005.
