Synchronous | Resemble | Documentation

The synchronous endpoint processes the entire input and returns a single audio payload—ideal for short prompts, notifications, or background jobs that do not require streaming.

Quick Example

curl --request POST "https://f.cluster.resemble.ai/synthesize" \
  -H "Authorization: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Accept-Encoding: gzip" \
  --data '{
    "voice_uuid": "55592656",
    "data": "Hello from Resemble!",
    "sample_rate": 48000,
    "output_format": "wav"
  }'

Decode the audio_content field from base64 to retrieve the raw audio bytes.

Endpoint

POST https://f.cluster.resemble.ai/synthesize

Request Headers

Header	Value	Description
`Authorization`	`YOUR_API_KEY`	API key from the dashboard.
`Content-Type`	`application/json`	JSON request body.
`Accept-Encoding`	`gzip`, `deflate`, or `br`	Optional compression.

Request Body

Field	Type	Required	Description
`voice_uuid`	string	Yes	Voice to synthesize.
`data`	string	Yes	Text or SSML to synthesize (≤ 2,000 characters).
`project_uuid`	string	No	Project to store the clip in.
`title`	string	No	Title for the generated clip.
`precision`	string	No	`MULAW`, `PCM_16`, `PCM_24`, `PCM_32` (default). Applies to WAV output.
`output_format`	string	No	`wav` (default) or `mp3`.
`sample_rate`	number	No	`8000`, `16000`, `22050`, `32000`, `44100`, or `48000`. Defaults to `48000`.
`use_hd`	boolean	No	Enables higher-definition synthesis with a small latency trade-off. Defaults to `false`.
`apply_custom_pronunciations`	boolean	No	When `true`, automatically applies your team’s custom pronunciations to matching words in the input text. Defaults to `false`.

Response

{
  "audio_content": "<base64>",
  "audio_timestamps": {
    "graph_chars": ["H", "e", "l", "l", "o"],
    "graph_times": [[0.0, 0.12], [0.12, 0.24], ...],
    "phon_chars": [],
    "phon_times": []
  },
  "duration": 1.68,
  "issues": [],
  "output_format": "wav",
  "sample_rate": 48000,
  "seed": 962692783,
  "success": true,
  "synth_duration": 1.64,
  "title": null
}

Field	Type	Description
`audio_content`	string	Base64-encoded audio bytes.
`audio_timestamps`	object	Timestamp arrays for graphemes and phonemes. Grapheme times use `[start, end]` pairs in seconds. Phoneme timestamp arrays may be empty.
`duration`	number	Final clip duration in seconds.
`issues`	array	Issues related to the request.
`output_format`	string	Echoes the requested format.
`sample_rate`	number	Echoes the requested sample rate.
`seed`	number	Random seed used for generation.
`success`	boolean	Whether the synthesis succeeded.
`synth_duration`	number	Raw synthesis time prior to post-processing.
`title`	string \| null	Title saved with the clip, or `null` if not provided.

Try it – Repeat the request above and decode audio_content locally:

curl --request POST "https://f.cluster.resemble.ai/synthesize" \
  -H "Authorization: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  --data '{
    "voice_uuid": "55592656",
    "data": "Hello from Resemble!",
    "sample_rate": 48000,
    "output_format": "wav"
  }' \
| jq -r '.audio_content' | base64 --decode > output.wav