JSON subtitle format

Reference · Last updated 2025

Overview

JSON is not a formal subtitle standard — each tool defines its own schema. But a common pattern has emerged: an array of cue objects, each with a start time, end time and text. This is useful for loading subtitles into JavaScript video players, processing them programmatically and exporting from subtitle tools.

Extension: .json
Complexity: Low
Browser support: Native (JSON.parse)

Common schema

[
  {
    "id": "1",
    "start": 1000,
    "end": 4000,
    "startTime": "00:00:01.000",
    "endTime": "00:00:04.000",
    "text": "Hello and welcome."
  },
  {
    "id": "2",
    "start": 5500,
    "end": 8750,
    "startTime": "00:00:05.500",
    "endTime": "00:00:08.750",
    "text": "This is the second cue."
  }
]

Fields

id — cue identifier (string).
start — start time in milliseconds (integer).
end — end time in milliseconds (integer).
startTime — start time as HH:MM:SS.mmm string (optional; for human readability).
endTime — end time as HH:MM:SS.mmm string (optional).
text — dialogue (string).

Only start, end and text are needed to reconstruct a subtitle file. id is useful for tracking. startTime and endTime are helpful for humans but redundant.

Alternate schemas

Different tools use different schemas. Common variations:

Field names: begin / finish or from / to instead of start / end.
Time units: seconds as floating-point numbers instead of milliseconds.
Format: object with a cues array instead of a top-level array.
Language: nested by language code for multi-language files.

Subtitle Convert accepts the common fields and falls back to time-string parsing when numeric fields are missing.

Use cases

JavaScript video players — loading subtitle cues into an in-browser player.
Data pipelines — processing subtitles programmatically without parsing text formats.
Language learning apps — extracting dialogue with timing for exercises.
Research — corpus analysis on dialogue data.

Converting between JSON and subtitle formats

Subtitle to JSON — export SRT or VTT cues as JSON.
JSON to SRT — rebuild SRT from JSON.