MODEL ID elevenlabs:20@1

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Eleven Monolingual v1

by ElevenLabs May 27, 2025

Eleven Monolingual v1 is an English only text to speech model from ElevenLabs. It focuses on simple natural delivery and stable output. Ideal for lightweight applications, legacy integrations, or projects that need predictable English voice synthesis with low complexity.

API Options

Platform-level options for task execution and delivery.

taskType string required value: audioInference: Identifier for the type of task being performed

taskUUID string required UUID v4: UUID v4 identifier for tracking tasks and matching async responses. Must be unique per task.

outputType string default: URL: Audio output type.

Allowed values 3 values

outputFormat string default: MP3

Specifies the file format of the generated output. The available values depend on the task type and the specific model's capabilities.

`MP3`: Compressed audio, smaller file size.
`WAV`: Uncompressed, high-quality audio.
`FLAC`: Lossless compression.
`OGG`: Open-source compressed audio format (Vorbis codec).

Allowed values 4 values

audioSettings object

Audio encoding settings for controlling the bitrate, number of channels, and sample rate of the generated audio. Only applicable for lossy output formats (MP3 and OGG). When using lossless formats (WAV or FLAC), this parameter must not be provided.

The available sample rates and valid bitrate ranges depend on the output format. For OGG, bitrate limits also vary by the number of channels.

MP3 bitrate limits

Bitrate limits for MP3 are the same regardless of mono or stereo.

Sample Rate	Min Bitrate	Max Bitrate
8,000 Hz	8 kbps	64 kbps
11,025 Hz	8 kbps	64 kbps
12,000 Hz	8 kbps	64 kbps
16,000 Hz	8 kbps	160 kbps
22,050 Hz	8 kbps	160 kbps
24,000 Hz	8 kbps	160 kbps
32,000 Hz	32 kbps	320 kbps
44,100 Hz	32 kbps	320 kbps
48,000 Hz	32 kbps	320 kbps

OGG bitrate limits — Mono (1 channel)

Sample Rate	Min Bitrate	Max Bitrate
8,000 Hz	8 kbps	40 kbps
12,000 Hz	16 kbps	48 kbps
16,000 Hz	16 kbps	96 kbps
24,000 Hz	16 kbps	80 kbps
48,000 Hz	32 kbps	224 kbps

OGG bitrate limits — Stereo (2 channels)

Sample Rate	Min Bitrate	Max Bitrate
8,000 Hz	16 kbps	80 kbps
12,000 Hz	16 kbps	96 kbps
16,000 Hz	24 kbps	192 kbps
24,000 Hz	32 kbps	160 kbps
48,000 Hz	48 kbps	256 kbps

Lossless formats: When outputFormat is set to WAV or FLAC, the audioSettings parameter is not available since these formats produce uncompressed or lossless audio with no configurable encoding settings.

Properties 3 properties

audioSettings » bitrate bitrate integer min: 8: Audio bitrate in kbps.

audioSettings » channels channels integer default: 2: Number of audio channels. 1 for mono, 2 for stereo.

Allowed values 2 values

audioSettings » sampleRate sampleRate integer: Audio sample rate in Hz.

webhookURL string URI

Specifies a webhook URL where JSON responses will be sent via HTTP POST when generation tasks complete. For batch requests with multiple results, each completed item triggers a separate webhook call as it becomes available.

Learn more 1 resource

Webhooks
PLATFORM

deliveryMethod string default: sync

Determines how the API delivers task results.

Allowed values 2 values

: Returns complete results directly in the API response.
: Returns an immediate acknowledgment with the task UUID. Poll for results using getResponse.

Learn more 1 resource

Task Polling
PLATFORM

uploadEndpoint string URI

Specifies a URL where the generated content will be automatically uploaded using the HTTP PUT method. The raw binary data of the media file is sent directly as the request body. For secure uploads to cloud storage, use presigned URLs that include temporary authentication credentials.

Common use cases:

Cloud storage: Upload directly to S3 buckets, Google Cloud Storage, or Azure Blob Storage using presigned URLs.
CDN integration: Upload to content delivery networks for immediate distribution.

// S3 presigned URL for secure upload
https://your-bucket.s3.amazonaws.com/generated/content.mp4?X-Amz-Signature=abc123&X-Amz-Expires=3600

// Google Cloud Storage presigned URL
https://storage.googleapis.com/your-bucket/content.jpg?X-Goog-Signature=xyz789

// Custom storage endpoint
https://storage.example.com/uploads/generated-image.jpg

The content data will be sent as the request body to the specified URL when generation is complete.

ttl integer min: 60: Time-to-live (TTL) in seconds for generated content. Only applies when outputType is URL.

includeCost boolean default: false: Include task cost in the response.

numberResults integer min: 1 max: 4 default: 1: Number of results to generate. Each result uses a different seed, producing variations of the same parameters.

Generation Parameters

Core parameters for controlling the generated content.

model string required value: elevenlabs:20@1

Identifier of the model to use for generation.

Learn more 3 resources

seed integer min: 0 max: 4294967295: Random seed for reproducible generation. When not provided, a random seed is generated in the unsigned 32-bit range.

speech object required

Settings for speech generation.

Properties 2 properties

speech » text text string max: 10000: Text to convert to speech.

speech » language language string min: 1: Language code for speech generation.

Allowed values 1 value

Provider Settings

Parameters specific to this model provider. These must be nested inside the providerSettings.elevenlabs object.

providerSettings » elevenlabs » textToSpeech textToSpeech object

Provider-specific settings for ElevenLabs text-to-speech generation.

Properties 5 properties

providerSettings » elevenlabs » textToSpeech » voiceSettings voiceSettings object

Voice settings overriding stored settings for the given voice. Applied only on the given request.

Properties 4 properties

providerSettings » elevenlabs » textToSpeech » voiceSettings » stability stability float min: 0 max: 1: Controls voice stability and randomness between each generation. Lower values introduce broader emotional range, higher values produce a more consistent tone.

providerSettings » elevenlabs » textToSpeech » voiceSettings » useSpeakerBoost useSpeakerBoost boolean: Boosts similarity to the original speaker at a slight increase in computational load and latency.

providerSettings » elevenlabs » textToSpeech » voiceSettings » similarityBoost similarityBoost float min: 0 max: 1: Controls how closely the AI adheres to the original voice when attempting to replicate it.

providerSettings » elevenlabs » textToSpeech » voiceSettings » style style float min: 0 max: 1: Controls style exaggeration of the voice. Higher values amplify the style of the original speaker but may increase latency.

providerSettings » elevenlabs » textToSpeech » previousText previousText string max: 1000: Text that came before the current request. Improves speech continuity when concatenating multiple generations.

providerSettings » elevenlabs » textToSpeech » nextText nextText string max: 1000: Text that comes after the current request. Improves speech continuity when concatenating multiple generations.

providerSettings » elevenlabs » textToSpeech » applyTextNormalization applyTextNormalization string default: auto

Controls text normalization behavior (e.g., spelling out numbers).

Allowed values 3 values

: Automatically decides whether to apply text normalization.
: Always applies text normalization.
: Skips text normalization entirely.

providerSettings » elevenlabs » textToSpeech » applyLanguageTextNormalization applyLanguageTextNormalization boolean default: false: Enables language-specific text normalization for proper pronunciation. Currently only supported for Japanese. Warning: can significantly increase latency.

taskType string required value: audioInference: Type of the task.

taskUUID string required UUID v4: UUID of the task.

audioUUID string required UUID v4: UUID of the output audio.

audioURL string URI: URL of the output audio.

audioBase64Data string: Base64-encoded audio data.

audioDataURI string URI: Data URI of the output audio.

seed integer: The seed used for generation. If none was provided, shows the randomly generated seed.

cost float: Task cost in USD. Present when includeCost is set to true in the request.

Text to Audio

Crackling Deep-Space Distress Log

0:00

Request

{
  "taskType": "audioInference",
  "taskUUID": "6ef33047-6d9c-4510-8cee-bd1f208d7486",
  "model": "elevenlabs:20@1",
  "seed": 46384,
  "speech": {
    "text": "Command, this is survey vessel Arden Nine. If this reaches anyone, our navigation array failed after the second flare. We are drifting beyond the mapped corridor with power restricted to life support, telemetry, and one narrow-band transmitter. The crew is conscious. Oxygen reserves are limited, but morale is holding. We have marked our current vector against the red giant in the Perseus reach and released three signal beacons at seven-minute intervals. Please advise any rescue traffic to avoid the debris field to our stern. Repeating final coordinates now. Arden Nine standing by.",
    "language": "en"
  },
  "providerSettings": {
    "elevenlabs": {
      "textToSpeech": {
        "voiceSettings": {
          "stability": 0.78,
          "similarityBoost": 0.72,
          "style": 0.22,
          "useSpeakerBoost": true
        },
        "applyTextNormalization": "auto",
        "previousText": "Emergency channel open. Priority traffic only.",
        "nextText": "End of transmission. Awaiting response."
      }
    }
  }
}

Response

{
  "taskType": "audioInference",
  "taskUUID": "6ef33047-6d9c-4510-8cee-bd1f208d7486",
  "audioUUID": "055acc7f-dcb5-43bb-afdd-407f2acac9fb",
  "audioURL": "https://am.runware.ai/audio/os/a23d05/ws/5/ai/055acc7f-dcb5-43bb-afdd-407f2acac9fb.mp3",
  "seed": 46384,
  "cost": 0.09136
}

Text to Audio

Antique Phonograph Museum Guide

0:00

Request

{
  "taskType": "audioInference",
  "taskUUID": "baec74ad-0310-4120-a3ca-3d8abc10c3c6",
  "model": "elevenlabs:20@1",
  "seed": 99331,
  "speech": {
    "text": "Welcome to Gallery Three, home of the singing machines. In front of you is an early phonograph with a polished brass horn and a hand-cranked motor. Visitors often expect a rich modern sound, but these devices produced a narrow, scratchy signal that listeners of the time still found astonishing. Imagine hearing a human voice replay itself from a wax cylinder for the very first time. To your left is a later home model, built to make recorded music part of ordinary evenings. Notice how the cabinet becomes more refined, hiding the mechanism inside furniture so the machine feels less industrial and more domestic. Before you move on, look closely at the tiny grooves in the recording medium. Those delicate lines carried speeches, comic routines, and parlor songs across years of handling and travel. When you are ready, continue to the next room for the early era of broadcast receivers.",
    "language": "en"
  },
  "providerSettings": {
    "elevenlabs": {
      "textToSpeech": {
        "voiceSettings": {
          "stability": 0.82,
          "similarityBoost": 0.72,
          "style": 0.18,
          "useSpeakerBoost": true
        },
        "applyTextNormalization": "auto",
        "previousText": "This wing explores inventions that changed how people listened at home.",
        "nextText": "The next section examines how radio transformed news, entertainment, and public life."
      }
    }
  }
}

Response

{
  "taskType": "audioInference",
  "taskUUID": "baec74ad-0310-4120-a3ca-3d8abc10c3c6",
  "audioUUID": "b26b0669-87c0-4ff9-b1ac-653c8011ffc3",
  "audioURL": "https://am.runware.ai/audio/os/a04d20/ws/5/ai/b26b0669-87c0-4ff9-b1ac-653c8011ffc3.mp3",
  "seed": 99331,
  "cost": 0.13675
}

Text to Audio

Subterranean Transit Safety Announcement

0:00

Request

{
  "taskType": "audioInference",
  "taskUUID": "bd9e333e-4f11-4e9c-8b44-cd6ed76e36dc",
  "model": "elevenlabs:20@1",
  "seed": 64131,
  "speech": {
    "text": "Attention passengers. This is a service update for Platform C. The 7:15 inbound train to Ashgrove has been delayed by approximately 12 minutes due to signal checks near Harbor Junction. For the fastest alternate route, board the 7:18 shuttle service from Bay 4 and transfer at Central Exchange. Please stand behind the yellow line, keep aisles clear, and allow exiting passengers to step off before boarding. If you require accessibility assistance, press the blue help point or speak with a station attendant. We appreciate your patience and cooperation.",
    "language": "en"
  },
  "providerSettings": {
    "elevenlabs": {
      "textToSpeech": {
        "voiceSettings": {
          "stability": 0.82,
          "similarityBoost": 0.72,
          "style": 0.18,
          "useSpeakerBoost": true
        },
        "applyTextNormalization": "on"
      }
    }
  }
}

Response

{
  "taskType": "audioInference",
  "taskUUID": "bd9e333e-4f11-4e9c-8b44-cd6ed76e36dc",
  "audioUUID": "a04c8311-2c32-4b32-b47b-60410014140f",
  "audioURL": "https://am.runware.ai/audio/os/a17d13/ws/5/ai/a04c8311-2c32-4b32-b47b-60410014140f.mp3",
  "seed": 64131,
  "cost": 0.08451
}

Text to Audio

Harbor Evacuation Ferry Bulletin

0:00

Request

{
  "taskType": "audioInference",
  "taskUUID": "04002268-d5f5-4e88-8b41-a12bac953653",
  "model": "elevenlabs:20@1",
  "seed": 75211,
  "speech": {
    "text": "Attention passengers at Pier Seven. Due to a chemical spill on the east access road, all private vehicle pickup has been suspended until further notice. Please remain inside the marked waiting zone and listen carefully for your boarding group. Families traveling with children, passengers using mobility aids, and anyone holding a blue priority ticket will board first for the 6:40 departure to North Haven. Group B will follow immediately after. Do not approach the loading ramp until your group is called. For your safety, leave all bicycles, carts, and oversized luggage against the orange barrier for crew inspection. If you feel dizzy, short of breath, or need medication from a stored bag, notify a dock attendant right away. Again, this is a controlled evacuation transfer to North Haven. Stay calm, keep the center aisle open, and await further instructions.",
    "language": "en"
  },
  "providerSettings": {
    "elevenlabs": {
      "textToSpeech": {
        "voiceSettings": {
          "stability": 0.82,
          "similarityBoost": 0.72,
          "style": 0.18,
          "useSpeakerBoost": true
        },
        "applyTextNormalization": "on"
      }
    }
  }
}

Response

{
  "taskType": "audioInference",
  "taskUUID": "04002268-d5f5-4e88-8b41-a12bac953653",
  "audioUUID": "689f9690-2d0b-4af6-98e2-a7672c88db5a",
  "audioURL": "https://am.runware.ai/audio/os/a10d08/ws/5/ai/689f9690-2d0b-4af6-98e2-a7672c88db5a.mp3",
  "seed": 75211,
  "cost": 0.13153
}