Closed captions toggle, open captions are baked in
One difference drives everything else. Closed captions can be turned on or off by the viewer; open captions are a permanent part of the video picture and can't be turned off, so they're visible to anyone watching (WebAIM). Closed captions ride in the signal or a separate file and get drawn at playback. Open captions skip that step entirely, rendered straight into the pixels before anyone presses play.
The FCC uses the same split. It defines closed captioning as "the visual display of the audio portion of video programming pursuant to the technical specifications" set out in its rules, and it allows open captioning or subtitles "in lieu of closed captioning" (47 CFR 79.1). Both carry the same spoken words as timed on-screen text. The only question is who controls whether they show.
Think of it as togglable versus painted-on. A closed caption is data your player renders, so you can switch it off, restyle it, or edit the text without touching the video. An open caption is already part of the frame: identical everywhere, with no decoding required.
Where each form earns its place
Open captions win on certainty. Because nothing has to decode or toggle, the text shows up on any platform, including a muted social feed that autoplays without sound. The trade-offs: fixed size and position, no viewer styling, and no off switch. Editing a typo means re-rendering the whole video, since the words are pixels now.
Closed captions win on control. CEA-708 decoders let viewers pick among eight fonts and 64 colors and vary the text size (47 CFR 79.103), options a burned-in caption can never offer. The text stays editable and searchable, and machines can index it. The catch is dependence on the player honoring the caption track. If a platform strips or garbles the sidecar, the words vanish.
A quick rule of thumb. Reach for open captions where you can't trust the player: muted autoplay clips, kiosks, digital signage, or hardware you don't control. Reach for closed captions on broadcast, streaming, and any site you own, wherever viewers want control and you want machine-readable text you can re-edit later.
The formats behind each: SRT, WebVTT, CEA-608 and 708
Broadcast captions run on two standards. CEA-608 (EIA-608, the old "line 21" system) carries analog closed captions in the vertical blanking interval of the NTSC signal. They sit on a fixed 15-row by 32-column grid, split across the C1 and C2 channels (47 CFR 15.119). CEA-708 (EIA-708-B) is the digital ATSC standard. Its decoders add the font and color control that 608's fixed grid never had (47 CFR 79.102, ANSI/CTA-708).
Online, the caption track is usually a file. WebVTT is a W3C format whose main job is the HTML track element, which overlays captions or subtitles on a web player from a .vtt file (W3C, MDN). If you run the site, WebVTT keeps viewers in control of font, size, and color. You can generate one straight from a recording with an audio-to-VTT export.
SubRip (.srt) is the most basic of the common sidecar formats (Matroska). Its cue timestamps put a comma before the three-digit milliseconds, like 00:02:17,440. That simplicity is why it travels well between players and platforms. When something won't read WebVTT, an audio-to-SRT export is the portable fallback.
What accessibility law actually requires
The law cares that accurate, synchronized captions exist, not whether they toggle. WCAG 2.1 Success Criterion 1.2.2 is a Level A requirement: captions for all prerecorded audio in synchronized media (W3C). Open or closed, either form meets it, as long as the captions are present, accurate, and in sync.
On US television, the bar is quantified. The FCC requires 100% of new, nonexempt English- and Spanish-language programming to be closed captioned on each channel (47 CFR 79.1). Under the 2010 CVAA, that duty extended to IP-delivered full-length programming that already aired on TV with captions (FCC 12-9 Report and Order, 47 CFR 79.4).
Beyond broadcast, two more rules reach most organizations. Section 508's Revised ICT Standards require electronic content to meet WCAG 2.0 Levels A and AA, which includes that captions criterion (U.S. Access Board). And the DOJ says the ADA covers state and local government web content, where videos are made accessible with accurate synchronized captions (ADA.gov).
Open vs closed captions: which should you use?
You don't always have to choose. Plenty of teams ship both: a burned-in version for social feeds and a closed-caption sidecar on the channel they own. The hybrid costs one extra export, and it means the words survive whether or not a given player honors the track.
Both start from the same raw material: an accurate, timed transcript. Get the timed, editable transcript first, then decide how to ship it. Export it as an SRT or WebVTT sidecar for closed captions, or drop it into your video editor to burn open captions into the frame. The transcript is the artifact; open versus closed is just how you deliver it.
