Broadcast and accessibility docs split captions by whether the viewer has a choice. Closed captions ride as a track and can be turned off. Open captions are in the picture — historically a hardware overlay, now almost always a burn into the file — and they stay up. Production people say burned-in. Delivery specs and RFPs still say open. Same object, two industries. SDH can be open or closed; the SDH part is the content (speech plus non-speech plus speaker IDs), not the switch.
Short-form wants open captions for a mechanical reason: mute autoplay will not enable a closed track. The look is part of the edit. Karaoke and word-highlight are open captions with a word clock. A platform-native layer is closed even when the app draws it by default, because a setting, a download, or another app can drop it.
The cost of open is that timing and placement freeze into pixels. A later trim is a new caption render, not a nudge of a sidecar. Lock the cut first. Keep the block off the safe area. If a master also needs a restylable track for a course player, export SRT from the same transcript rather than treating the burn as the only file.
In practice
- When a brief says open captions, deliver a burn, not a .srt and a note that the player can turn it on.
- Lock picture before you burn. Open captions are pixels.
- If the same master needs a toggleable track, make the sidecar from the transcript; do not extract type from the flatten.
The mistake to avoid
Hearing 'open captions' and uploading a closed track with captions-on as the default. Open means the viewer has no off switch.
Where you will run into it
- Add Captions to a Video — Speech in, styled subtitles out — no manual timing.
- AI Caption Generator — Drop a video, get timed captions. Free, on your device, no upload.
Related terms
Burned-in captions
Burned-in captions meaning: subtitles rendered into pixels, so viewers cannot turn them off or lose them on re-upload. Closed captions are a separate track.
Closed captions
Closed captions are a separate subtitle track the player draws, which the viewer can switch off and which each platform styles itself.
SDH
SDH is a caption track that includes speech and non-speech audio — [door slams], [music], speaker IDs — so the file is usable without sound.
Hook rate
Hook rate meaning: the share of people shown a video who are still watching a few seconds in. It grades the opening, not the body.
Retention curve
Retention curve meaning: how many starters are still watching at each second. Watch time is the area under that curve.
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