> ## Documentation Index
> Fetch the complete documentation index at: https://typecast.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Timestamps & captions

> Generate timestamp alignment data, SRT subtitles, or WebVTT captions with the CLI.

The CLI can call Typecast Timestamp TTS and save alignment data alongside the generated audio. Use this when an agent needs subtitles for Shorts, caption timing for social video, karaoke-style highlights, or lip-sync metadata.

## Generate subtitles

```bash theme={null}
# Save audio and SRT subtitles
cast "Hello, world. This is a test." \
  --out hello.wav \
  --timestamps-out hello.srt

# Save audio and WebVTT subtitles
cast "Hello, world. This is a test." \
  --out hello.wav \
  --timestamps-out hello.vtt \
  --timestamps-format vtt
```

When `--timestamps-format` is omitted, CLI infers `srt` or `vtt` from the `--timestamps-out` extension and falls back to `json`.

## Save raw timestamp JSON

```bash theme={null}
cast "Hello, world. This is a test." \
  --out hello.wav \
  --timestamps-out hello.timestamps.json
```

JSON is useful when another tool will create captions, animate text, or align visuals manually.

## Choose granularity

```bash theme={null}
cast "Hello, world." \
  --out hello.wav \
  --timestamps-out hello.srt \
  --granularity both
```

For languages without whitespace between words, such as Japanese (`jpn`) or Chinese (`zho`), use character-level timestamps for usable subtitle timing:

```bash theme={null}
cast "こんにちは。世界。" \
  --language jpn \
  --out hello.wav \
  --timestamps-out hello.srt
```

## Caption workflow for agents

```text theme={null}
Create narration audio and captions from script.txt.
Use the CLI.
Write audio to ./video/voiceover.wav.
Write subtitles to ./video/voiceover.srt.
Keep the subtitle file next to the audio file.
```

## Output choices

| Output  | Use when                                                              |
| ------- | --------------------------------------------------------------------- |
| `.srt`  | Video editors, Shorts/Reels/TikTok caption import                     |
| `.vtt`  | Web video players and browser-based previews                          |
| `.json` | Custom rendering, karaoke highlights, lip-sync, downstream automation |

<Tip>
  For social video, generate captions in the same step as audio. It keeps the final narration and subtitle timing tied to the exact same synthesis result.
</Tip>