--- title: Inworld TTS-1.5 Max | Runware Docs url: https://runware.ai/docs/models/inworld-tts-1-5-max description: High-fidelity expressive text-to-speech with rich prosody and multilingual support --- # Inworld TTS-1.5 Max ![Inworld TTS-1.5 Max](https://assets.runware.ai/covers/inworld-tts-1-5-max.jpg) Inworld TTS-1.5 Max is a high-fidelity text-to-speech model engineered for expressive voice synthesis with rich prosody, nuanced emotional range, and broadcast-ready audio quality. It supports a wide set of languages and delivers more natural pronunciation and expressive variation suitable for narration, content creation, and immersive character voices. The Max variant prioritizes audio quality and expressiveness while still supporting responsive generation. - **Status**: live - **ID**: `inworld:tts@1.5-max` - Try in Playground - **Creator**: Inworld AI - **Release Date**: January 21, 2026 - **Capabilities**: Text to Audio, Checkpoint ## Pricing $0.00005 per character · ~8s per request **5 example generations** - [text-to-audio](https://runware.ai/docs/models/inworld-tts-1-5-max/examples#example-championship-pinball-broadcast-vocal-stinger): `$0.00455` (~3s) - [text-to-audio](https://runware.ai/docs/models/inworld-tts-1-5-max/examples#example-seed-library-vocal-audio-logo): `$0.00515` (~3s) - [text-to-audio](https://runware.ai/docs/models/inworld-tts-1-5-max/examples#example-antarctic-field-lab-pa-bed): `$0.0251` (~8s) - [text-to-audio](https://runware.ai/docs/models/inworld-tts-1-5-max/examples#example-cold-storage-energy-explainer-voiceover): `$0.0297` (~9s) - [text-to-audio](https://runware.ai/docs/models/inworld-tts-1-5-max/examples#example-urban-forestry-podcast-cold-open): `$0.0297` (~9s) times vary, measured end to end · [How pricing works](https://runware.ai/docs/platform/pricing) ## Request Parameters **API Options** Platform-level options for task execution and delivery. ### [taskType](https://runware.ai/docs/models/inworld-tts-1-5-max#request-tasktype) - **Type**: `string` - **Required**: true - **Value**: `audioInference` Identifier for the type of task being performed ### [taskUUID](https://runware.ai/docs/models/inworld-tts-1-5-max#request-taskuuid) - **Type**: `string` - **Required**: true - **Format**: `UUID v4` UUID v4 identifier for tracking tasks and matching async responses. Must be unique per task. ### [outputType](https://runware.ai/docs/models/inworld-tts-1-5-max#request-outputtype) - **Type**: `string` - **Default**: `URL` Audio output type. **Allowed values**: `URL` `base64Data` `dataURI` ### [outputFormat](https://runware.ai/docs/models/inworld-tts-1-5-max#request-outputformat) - **Type**: `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**: `MP3` `WAV` `FLAC` `OGG` ### [audioSettings](https://runware.ai/docs/models/inworld-tts-1-5-max#request-audiosettings) - **Path**: `audioSettings.bitrate` - **Type**: `object (3 properties)` 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 | > [!NOTE] > **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. #### [bitrate](https://runware.ai/docs/models/inworld-tts-1-5-max#request-audiosettings-bitrate) - **Path**: `audioSettings.bitrate` - **Type**: `integer` - **Min**: `1` Target audio bitrate in kbps. Constraints depend on the output format. #### [sampleRate](https://runware.ai/docs/models/inworld-tts-1-5-max#request-audiosettings-samplerate) - **Path**: `audioSettings.sampleRate` - **Type**: `integer` - **Min**: `1000` Audio sample rate in Hz. #### [channels](https://runware.ai/docs/models/inworld-tts-1-5-max#request-audiosettings-channels) - **Path**: `audioSettings.channels` - **Type**: `integer` - **Default**: `2` Number of audio channels in the generated output (1 for Mono, 2 for Stereo). **Allowed values**: `1` `2` ### [webhookURL](https://runware.ai/docs/models/inworld-tts-1-5-max#request-webhookurl) - **Type**: `string` - **Format**: `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](https://runware.ai/docs/platform/webhooks) (platform) ### [deliveryMethod](https://runware.ai/docs/models/inworld-tts-1-5-max#request-deliverymethod) - **Type**: `string` - **Default**: `sync` Determines how the API delivers task results. **Allowed values**: - `sync` Returns complete results directly in the API response. - `async` Returns an immediate acknowledgment with the task UUID. Poll for results using getResponse. **Learn more** (1 resource): - [Task Polling](https://runware.ai/docs/platform/task-polling) (platform) ### [uploadEndpoint](https://runware.ai/docs/models/inworld-tts-1-5-max#request-uploadendpoint) - **Type**: `string` - **Format**: `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. ```text // 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](https://runware.ai/docs/models/inworld-tts-1-5-max#request-ttl) - **Type**: `integer` - **Min**: `60` Time-to-live (TTL) in seconds for generated content. Only applies when `outputType` is `URL`. ### [includeCost](https://runware.ai/docs/models/inworld-tts-1-5-max#request-includecost) - **Type**: `boolean` Include task cost in the response. ### [numberResults](https://runware.ai/docs/models/inworld-tts-1-5-max#request-numberresults) - **Type**: `integer` - **Min**: `1` - **Max**: `4` - **Default**: `1` Number of results to generate. Each result uses a different seed, producing variations of the same parameters. **Core Parameters** Primary parameters that define the task output. ### [model](https://runware.ai/docs/models/inworld-tts-1-5-max#request-model) - **Type**: `string` - **Required**: true - **Value**: `inworld:tts@1.5-max` Identifier of the model to use for generation. **Learn more** (3 resources): - [Text To Image: Model Selection](https://runware.ai/docs/learn/text-to-image#model-selection) (learn) - [Image Inpainting: Model Specialized Inpainting Models](https://runware.ai/docs/learn/image-inpainting#model-specialized-inpainting-models) (learn) - [Image Outpainting: Other Critical Parameters](https://runware.ai/docs/learn/image-outpainting#other-critical-parameters) (learn) ### [speech](https://runware.ai/docs/models/inworld-tts-1-5-max#request-speech) - **Path**: `speech.text` - **Type**: `object (3 properties)` - **Required**: true Settings for speech generation. #### [text](https://runware.ai/docs/models/inworld-tts-1-5-max#request-speech-text) - **Path**: `speech.text` - **Type**: `string` - **Required**: true - **Min**: `2` - **Max**: `2000` Text to convert to speech. #### [voice](https://runware.ai/docs/models/inworld-tts-1-5-max#request-speech-voice) - **Path**: `speech.voice` - **Type**: `string` - **Required**: true Voice identifier to use for speech generation. **Allowed values**: `Loretta` `Darlene` `Marlene` `Hank` `Evelyn` `Celeste` `Pippa` `Tessa` `Liam` `Callum` `Hamish` `Abby` `Graham` `Rupert` `Mortimer` `Snik` `Anjali` `Saanvi` `Arjun` `Claire` `Oliver` `Simon` `Elliot` `James` `Serena` `Gareth` `Vinny` `Lauren` `Jessica` `Ethan` `Tyler` `Jason` `Chloe` `Veronica` `Victoria` `Miranda` `Sebastian` `Victor` `Malcolm` `Kayla` `Nate` `Jake` `Brian` `Amina` `Kelsey` `Derek` `Grant` `Evan` `Alex` `Ashley` `Craig` `Deborah` `Dennis` `Edward` `Elizabeth` `Hades` `Julia` `Pixie` `Mark` `Olivia` `Priya` `Ronald` `Sarah` `Shaun` `Theodore` `Timothy` `Wendy` `Dominus` `Hana` `Clive` `Carter` `Blake` `Luna` #### [speed](https://runware.ai/docs/models/inworld-tts-1-5-max#request-speech-speed) - **Path**: `speech.speed` - **Type**: `float` - **Min**: `0.5` - **Max**: `1.5` - **Step**: `0.1` - **Default**: `1` Playback speed of the generated speech. **Settings** Technical parameters to fine-tune the inference process. These must be nested inside the \`settings\` object. ### [temperature](https://runware.ai/docs/models/inworld-tts-1-5-max#request-settings-temperature) - **Path**: `settings.temperature` - **Type**: `float` - **Min**: `0.1` - **Max**: `2` - **Step**: `0.01` - **Default**: `1.1` Controls randomness in generation. Lower values produce more deterministic outputs, higher values increase variation and creativity. ### [textNormalization](https://runware.ai/docs/models/inworld-tts-1-5-max#request-settings-textnormalization) - **Path**: `settings.textNormalization` - **Type**: `boolean` Expands numbers, dates, abbreviations before speech generation. ## Response Parameters ### [taskType](https://runware.ai/docs/models/inworld-tts-1-5-max#response-tasktype) - **Type**: `string` - **Required**: true - **Value**: `audioInference` Identifier for the type of task this response belongs to. ### [taskUUID](https://runware.ai/docs/models/inworld-tts-1-5-max#response-taskuuid) - **Type**: `string` - **Required**: true - **Format**: `UUID v4` UUID v4 identifier echoed from the original request, used to match async responses to their tasks. ### [audioUUID](https://runware.ai/docs/models/inworld-tts-1-5-max#response-audiouuid) - **Type**: `string` - **Required**: true - **Format**: `UUID v4` UUID of the output audio. ### [audioURL](https://runware.ai/docs/models/inworld-tts-1-5-max#response-audiourl) - **Type**: `string` - **Format**: `uri` URL of the output audio. ### [audioBase64Data](https://runware.ai/docs/models/inworld-tts-1-5-max#response-audiobase64data) - **Type**: `string` Base64-encoded audio data. ### [audioDataURI](https://runware.ai/docs/models/inworld-tts-1-5-max#response-audiodatauri) - **Type**: `string` - **Format**: `uri` Data URI of the output audio. ### [seed](https://runware.ai/docs/models/inworld-tts-1-5-max#response-seed) - **Type**: `integer` The seed used for generation. If none was provided, shows the randomly generated seed. ### [cost](https://runware.ai/docs/models/inworld-tts-1-5-max#response-cost) - **Type**: `float` Task cost in USD. Present when `includeCost` is set to `true` in the request. ## Examples ### text-to-audio (text-to-audio) [Listen to audio](https://assets.runware.ai/examples/inworld-tts-1-5-max/99c0ebef-6421-409f-9f20-eef80b79fec3.mp3) > **Prompt**: Your freezers work around the clock. But the price of powering them changes by the hour. A thermal battery turns that problem into an opportunity. When electricity is cleaner and less expensive, the system stores energy as cold. Then, during peak demand, it keeps your warehouse at the right temperature while compressors use less power. No change to daily operations. No compromise on food safety. Just steadier energy use, lower peak charges, and more flexibility when the grid is under pressure. Because in cold storage, timing matters — for every shipment, every degree, and every kilowatt. ```json { "taskType": "audioInference", "taskUUID": "76e6ba1a-535f-40dc-a6f8-7d84569eab50", "audioSettings": { "bitrate": 192, "sampleRate": 48000, "channels": 2 }, "model": "inworld:tts@1.5-max", "speech": { "text": "Your freezers work around the clock. But the price of powering them changes by the hour. A thermal battery turns that problem into an opportunity. When electricity is cleaner and less expensive, the system stores energy as cold. Then, during peak demand, it keeps your warehouse at the right temperature while compressors use less power. No change to daily operations. No compromise on food safety. Just steadier energy use, lower peak charges, and more flexibility when the grid is under pressure. Because in cold storage, timing matters — for every shipment, every degree, and every kilowatt.", "voice": "Claire", "speed": 1 }, "settings": { "temperature": 1.1, "textNormalization": true } } ``` --- ### text-to-audio (text-to-audio) [Listen to audio](https://assets.runware.ai/examples/inworld-tts-1-5-max/ba5d55af-327e-4b77-b82e-845c361be4c7.mp3) > **Prompt**: Tilt warning cleared—multiball is live! You're back at the 2026 World Pinball Championship. ```json { "taskType": "audioInference", "taskUUID": "5f5adde3-9f1d-43ad-8e48-6ff022fb31bb", "audioSettings": { "bitrate": 192, "sampleRate": 48000, "channels": 2 }, "model": "inworld:tts@1.5-max", "speech": { "text": "Tilt warning cleared—multiball is live! You're back at the 2026 World Pinball Championship.", "voice": "Loretta", "speed": 1 }, "settings": { "temperature": 1.1, "textNormalization": true } } ``` --- ### text-to-audio (text-to-audio) [Listen to audio](https://assets.runware.ai/examples/inworld-tts-1-5-max/c0353397-4c6b-450b-a704-d84d40575d46.mp3) > **Prompt**: One city block, forty-seven honey locusts, and a maintenance bill nobody budgeted for. So, who decides what a street tree is worth before the next heat wave tests it? This is Canopy Ledger, the show where urban forestry meets public money. I’m Mara Chen. Today, we’re following a single sapling from nursery bid to sidewalk—and asking why the cheapest tree can become the most expensive one on the block. You’ll hear from a city arborist, a procurement officer, and the contractor watering 18,000 new trees through August. First, though: the tiny line item that changed an entire planting plan. ```json { "taskType": "audioInference", "taskUUID": "e1406f38-f321-44d0-bcf5-a6e449d2e8c9", "audioSettings": { "bitrate": 192, "sampleRate": 48000, "channels": 2 }, "model": "inworld:tts@1.5-max", "speech": { "text": "One city block, forty-seven honey locusts, and a maintenance bill nobody budgeted for. So, who decides what a street tree is worth before the next heat wave tests it? This is Canopy Ledger, the show where urban forestry meets public money. I’m Mara Chen. Today, we’re following a single sapling from nursery bid to sidewalk—and asking why the cheapest tree can become the most expensive one on the block. You’ll hear from a city arborist, a procurement officer, and the contractor watering 18,000 new trees through August. First, though: the tiny line item that changed an entire planting plan.", "voice": "Loretta", "speed": 1 }, "settings": { "temperature": 1.1, "textNormalization": true } } ``` --- ### text-to-audio (text-to-audio) [Listen to audio](https://assets.runware.ai/examples/inworld-tts-1-5-max/8d8b8b1c-fa43-42bf-9256-d3fb983ed02d.mp3) > **Prompt**: Attention, Halley field team. The 18:40 surface check is complete. Exterior temperature is minus 31 degrees Celsius; wind is holding at 42 kilometers per hour. Visibility beyond Marker 6 is now poor. Secure loose instruments, close the west airlock manually, and log all departures with Operations. Dr. Imani, your ice-core transfer is cleared for Cold Store B. Power will shift to night load in ten minutes. Please finish nonessential equipment cycles now. The next weather update will follow at 19:00. ```json { "taskType": "audioInference", "taskUUID": "1a4787b1-968c-4c50-be7f-cc18a6f1d815", "audioSettings": { "bitrate": 192, "sampleRate": 48000, "channels": 2 }, "model": "inworld:tts@1.5-max", "speech": { "text": "Attention, Halley field team. The 18:40 surface check is complete. Exterior temperature is minus 31 degrees Celsius; wind is holding at 42 kilometers per hour. Visibility beyond Marker 6 is now poor. Secure loose instruments, close the west airlock manually, and log all departures with Operations. Dr. Imani, your ice-core transfer is cleared for Cold Store B. Power will shift to night load in ten minutes. Please finish nonessential equipment cycles now. The next weather update will follow at 19:00.", "voice": "Loretta", "speed": 1 }, "settings": { "temperature": 1.1, "textNormalization": true } } ``` --- ### text-to-audio (text-to-audio) [Listen to audio](https://assets.runware.ai/examples/inworld-tts-1-5-max/294e7d65-3004-4369-8dc3-66960d3c46ef.mp3) > **Prompt**: Borrow a seed. Grow a story. Bring the future back—one bright handful at a time. The City Seed Library. ```json { "taskType": "audioInference", "taskUUID": "10fc6b3b-b7fc-4503-a405-d914b8f393dc", "audioSettings": { "bitrate": 192, "sampleRate": 48000, "channels": 2 }, "model": "inworld:tts@1.5-max", "speech": { "text": "Borrow a seed. Grow a story. Bring the future back—one bright handful at a time. The City Seed Library.", "voice": "Loretta", "speed": 1 }, "settings": { "temperature": 1.1, "textNormalization": true } } ``` --- [Listen to audio](https://assets.runware.ai/examples/inworld-tts-1-5-max/625af8f2-fce4-4bcc-b715-d052ed15a22c.mp3) > **Prompt**: When the last train disappeared into the rain, Elena remained alone on the platform, clutching a letter softened by the storm. She had waited ten years for this moment, rehearsing a hundred different greetings, but now that the city lights trembled in the puddles and the night smelled of iron and sea salt, all her words felt small. Then she heard footsteps behind her—slow, familiar, impossible—and the world seemed to hold its breath. ```json { "taskType": "audioInference", "taskUUID": "3ccb5b6a-760e-41d8-a780-c0557bb1c2d5", "model": "inworld:tts@1.5-max", "audioSettings": { "bitrate": 192, "sampleRate": 48000, "channels": 2 }, "speech": { "text": "When the last train disappeared into the rain, Elena remained alone on the platform, clutching a letter softened by the storm. She had waited ten years for this moment, rehearsing a hundred different greetings, but now that the city lights trembled in the puddles and the night smelled of iron and sea salt, all her words felt small. Then she heard footsteps behind her—slow, familiar, impossible—and the world seemed to hold its breath.", "voice": "Serena", "speed": 0.9 }, "settings": { "temperature": 1.12 } } ``` --- [Listen to audio](https://assets.runware.ai/examples/inworld-tts-1-5-max/9b943f81-a2ee-4e29-8734-03b0215b86b3.mp3) > **Prompt**: When the storm finally loosened its grip on the valley, Mira stepped out onto the rain-slick stones and listened. No thunder. No shouting wind. Only the soft dripping of water from the pine branches and, somewhere in the silver fog below, the lonely bell of the harbor lighthouse calling through the dawn. She drew a careful breath, tasted salt and cedar in the air, and unfolded the letter she had carried across three countries. The ink had run at the edges, but the final line was still clear: When the sea grows quiet, come find me. ```json { "taskType": "audioInference", "taskUUID": "0fa1ab9f-3ed8-4b8b-aa9c-540b9eb6f07a", "model": "inworld:tts@1.5-max", "audioSettings": { "bitrate": 192, "sampleRate": 48000, "channels": 2 }, "speech": { "text": "When the storm finally loosened its grip on the valley, Mira stepped out onto the rain-slick stones and listened. No thunder. No shouting wind. Only the soft dripping of water from the pine branches and, somewhere in the silver fog below, the lonely bell of the harbor lighthouse calling through the dawn. She drew a careful breath, tasted salt and cedar in the air, and unfolded the letter she had carried across three countries. The ink had run at the edges, but the final line was still clear: When the sea grows quiet, come find me.", "voice": "Serena", "speed": 0.9 }, "settings": { "temperature": 1.05 } } ``` --- [Listen to audio](https://assets.runware.ai/examples/inworld-tts-1-5-max/83848a31-3422-4fa1-83dd-4203974f6340.mp3) > **Prompt**: When the last ember faded, the kingdom did not fall in silence. It answered with steel, with thunder, and with the beating hearts of those who refused to kneel. Beyond the black cliffs, beneath a sky split by lightning, one rider carried the map, the oath, and the final spark of hope. By dawn, legends would awaken. By nightfall, the world would remember their names. ```json { "taskType": "audioInference", "taskUUID": "f3d5f422-48f8-407b-bcd1-5ca792df673d", "model": "inworld:tts@1.5-max", "audioSettings": { "bitrate": 192, "sampleRate": 48000, "channels": 2 }, "speech": { "text": "When the last ember faded, the kingdom did not fall in silence. It answered with steel, with thunder, and with the beating hearts of those who refused to kneel. Beyond the black cliffs, beneath a sky split by lightning, one rider carried the map, the oath, and the final spark of hope. By dawn, legends would awaken. By nightfall, the world would remember their names.", "voice": "Sebastian", "speed": 0.9 }, "settings": { "temperature": 1.12 } } ``` --- [Listen to audio](https://assets.runware.ai/examples/inworld-tts-1-5-max/32ae2e7a-b30d-4ea7-9adf-cdf3c9a12ed4.mp3) > **Prompt**: When the last train vanished into the fog, Mara stepped onto the silent platform and unfolded the letter one final time. The ink had faded, but the promise still burned between the lines: at midnight, under the station clock, the truth would finally arrive. Around her, the city held its breath. Then, from somewhere deep in the mist, came the slow echo of approaching footsteps. ```json { "taskType": "audioInference", "taskUUID": "1cf6413f-da48-42ba-9ded-515c239a8128", "model": "inworld:tts@1.5-max", "audioSettings": { "bitrate": 192, "sampleRate": 48000, "channels": 2 }, "speech": { "text": "When the last train vanished into the fog, Mara stepped onto the silent platform and unfolded the letter one final time. The ink had faded, but the promise still burned between the lines: at midnight, under the station clock, the truth would finally arrive. Around her, the city held its breath. Then, from somewhere deep in the mist, came the slow echo of approaching footsteps.", "voice": "Celeste", "speed": 0.9 }, "settings": { "temperature": 1.08 } } ```