JSON to TTML
Or paste subtitle text
What this conversion changes
1 thing is dropped or needs a decision
- Karaoke
karaoke timing (per-syllable highlighting)
This list comes from the capability matrix for these two formats, not from the particular file you loaded. A specific file may lose more if it uses features the format allows but the matrix does not model.
This page converts JSON to TTML. Drop a file in — or paste the text — and you get the TTML version back. The conversion runs entirely in your browser, so nothing is uploaded and no account is needed.
These two formats do not store the same things, and the difference is not cosmetic: karaoke has nowhere to go in TTML. The list above comes from what the two formats can each express rather than from your file, so it is the same answer before you load anything.
One file is fine, and so is a whole season: the queue works through them in order and the results come down together as a single ZIP.
Examples
A typical JSON file, converted to TTML
Input
{
"version": 1,
"title": "Fixture: typical",
"fps": 25,
"styles": {
"Default": {
"name": "Default",
"fontFamily": "Arial",
"fontSize": 20,
"primaryColor": "#FFFFFF",
"bold": false,
"italic": false
}
},
"generator": "subtitlematrix fixtures",
"cues": [
{
"id": "1",
"start": 0,
"end": 2000,
"lines": [
"Hello world.",
"Second line."
],
"style": "Default",
"position": {
"x": 100,
"y": 200,
"align": "center"
}
},
{
"id": "2",
"start": 2500,
"end": 4000,
"lines": [
"Plain line.",
{
"text": "Styled line.",
"tags": [
{
"kind": "italic",
"start": 0,
"end": 6
}
]
}
]
},
{
"id": "3",
"start": 4500,
"end": 6000,
"lines": [
"Roger: I am here."
],
"speaker": "Roger"
}
]
}
Output
<?xml version="1.0" encoding="UTF-8"?>
<tt xmlns="http://www.w3.org/ns/ttml" xmlns:tts="http://www.w3.org/ns/ttml#styling">
<body>
<p begin="00:00:00.000" end="00:00:02.000">Hello world.<br/>Second line.</p>
<p begin="00:00:02.500" end="00:00:04.000">Plain line.<br/><span tts:fontStyle="italic">Styled</span> line.</p>
<p begin="00:00:04.500" end="00:00:06.000">Roger: I am here.</p> </body>
</tt>
Dropped in this output: karaoke. Everything else matches line for line.
The same conversion on an awkward input
Input
[
{ "start": 0, "end": 1000, "lines": ["First."] },
{ "start": 1000, "end": 2000, "text": "Second." },
"not an object",
{ "start": 2000, "end": 3000, "lines": ["Third."], "class": "top" }
]
Output
<?xml version="1.0" encoding="UTF-8"?>
<tt xmlns="http://www.w3.org/ns/ttml" xmlns:tts="http://www.w3.org/ns/ttml#styling">
<body>
<p begin="00:00:00.000" end="00:00:01.000">First.</p>
<p begin="00:00:01.000" end="00:00:02.000">Second.</p>
<p begin="00:00:02.000" end="00:00:03.000">Third.</p> </body>
</tt>
This is the kind of damage real files have — mixed line endings, stray whitespace, fields left empty. Compare it with the tidy example above to see what the parser forgives.
Frequently asked questions
What happens to karaoke timing from JSON to TTML?
The timing goes; the words stay. Karaoke lives in the karaoke spans a JSON cue carries, which mark when each syllable lights up, and TTML has no way to record a moment inside a line — so the marks come off and the syllables arrive as ordinary TTML text.
What does the output look like when JSON becomes TTML?
Like TTML: no cue numbers: every subtitle is a `<p>` element with `begin` and `end` attributes, nested in a `<body>` (and usually a `<div>`), with an XML declaration above the whole document. Every JSON cue becomes one TTML cue, in the same order, with the same text.
Are the JSON timings exact in the TTML file?
Yes, to the millisecond — which is as fine as either format goes. JSON writes a moment as `4126` and TTML writes the same moment as `00:00:04.126`; nothing is rounded or shifted between the two, and a cue that was on screen for 2.9 seconds still is.
How does a two-line JSON cue come out in TTML?
As two lines with a `<br/>` between them, which is how TTML writes a hard line break. The pairing survives — the two JSON lines still belong to one subtitle in the TTML output, and a player shows them together.
Do JSON cues keep their order in the TTML output?
Yes, and they are sorted by start time on the way — earliest first, which is how every format here expects them and how players read them. If your JSON file listed its cues out of sequence, the TTML output puts them back in order; that is a change to the file's structure rather than its content, and it is deliberate.
Can I convert the TTML back to JSON?
Yes, and it has its own list: converting TTML to JSON drops format-specific content. That list is different from the one above because the two formats keep different things.
Does the TTML output keep the JSON file's encoding?
No — the output is UTF-8, with Unix line endings and no byte-order mark, whatever the JSON file used. A file that arrives in UTF-16, or in a Windows single-byte encoding, is decoded on the way in (the result panel says so when that happens); what comes out is always the same UTF-8 TTML.