Cos'è un file di sottotitoli JSON3? Formato YouTube

JSON3 is the internal subtitle format used by YouTube to store and deliver captions. It is a JSON-based format where each caption event has precise millisecond timing, word-level offsets, and text segments. AllSubConverter can convert JSON3 to SRT, VTT, LRC, and other formats.

What Does JSON3 Mean?

JSON3 refers to the JSON-based timedtext format used by YouTube's captioning system. Unlike plain-text formats such as SRT, JSON3 stores caption data as structured JSON objects with word-level timing, styling metadata, and automatic caption alignment.

How JSON3 Files Work

A JSON3 file contains an "events" array where each event represents a caption cue with start time (tStartMs), duration (dDurationMs), and text segments (segs). Individual segments can include tOffsetMs for word-level timing precision.

JSON3 File Structure

{
  "events": [
    {
      "tStartMs": 0,
      "dDurationMs": 3120,
      "segs": [
        { "utf8": "Hi " },
        { "utf8": "everyone." }
      ]
    },
    {
      "tStartMs": 3120,
      "dDurationMs": 4840,
      "segs": [
        { "utf8": "In " },
        { "tOffsetMs": 640, "utf8": "video," }
      ]
    }
  ]
}

Convert JSON3 to Other Formats

AllSubConverter supports converting JSON3 to all major subtitle formats. Choose a conversion tool below to get started: