CEA-608
CEA-608 (Line 21 captions)
The original US closed-caption standard for analog NTSC TV. Now used as embedded text tracks inside MP4 / TS broadcast files.
In depth
CEA-608 (also called Line 21 captions) is the closed-caption standard developed for analog NTSC television in the 1980s. It encodes captions in line 21 of the vertical blanking interval. Modern usage: CEA-608 lives on as an embedded text track inside MP4, MXF, and MPEG-TS broadcast deliverables. Most US broadcast networks still require CEA-608 / 708 captions on submitted content.
When to use it
Use CEA-608 when delivering to US broadcast TV. For streaming, web, and social, prefer SRT/VTT/ASS — CEA-608's character set and styling are decades behind modern formats.
Frequently asked
What's the difference between CEA-608 and CEA-708?+
CEA-708 is the digital ATSC successor to CEA-608. It supports more characters, more styling, and multiple language tracks. Most broadcast deliverables include both.
Can I use CEA-608 for YouTube?+
YouTube accepts SRT/VTT and converts internally. Don't deliver CEA-608 directly — convert to SRT first.