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

# API Changes

Starting June 1, 2026, we are discontinuing several models, snapshots, and languages, and removing voice embeddings from our voice API. Migrate to `sonic-3.5` for improved naturalness, 42-language support, and fine-grained controls.

## Deprecated models and languages

You can check if you're making requests to deprecated models on [play.cartesia.ai/deprecation/traffic](https://play.cartesia.ai/deprecation/traffic).

### Fully deprecated models

These models will stop serving requests on June 1, 2026.

| Model                | Snapshots affected       | Deprecated languages |
| -------------------- | ------------------------ | -------------------- |
| `sonic`              | All                      | All                  |
| `sonic-english`      | —                        | All                  |
| `sonic-multilingual` | —                        | All                  |
| `sonic-2`            | `sonic-2-2025-03-07`     | All                  |
| `sonic-turbo`        | `sonic-turbo-2025-03-07` | All                  |

### Partially deprecated models

These models will continue to serve a reduced set of languages. The languages listed below will be discontinued on June 1, 2026.

| Model         | Snapshots affected                                               | Deprecated languages       |
| ------------- | ---------------------------------------------------------------- | -------------------------- |
| `sonic-2`     | `sonic-2-2025-04-16`, `sonic-2-2025-05-08`, `sonic-2-2025-06-11` | it, nl, pl, ru, sv, tr, hi |
| `sonic-turbo` | `sonic-turbo-2025-06-04`                                         | it, nl, pl, ru, sv, tr     |

## Stable offerings

The following will remain available beyond June 1.

| Model         | Snapshots                                                        | Supported Languages                                                                               |
| ------------- | ---------------------------------------------------------------- | ------------------------------------------------------------------------------------------------- |
| `sonic-3`     | All                                                              | 42 languages — [full list](/build-with-cartesia/tts-models/older-models#language-support-sonic-3) |
| `sonic-2`     | `sonic-2-2025-04-16`, `sonic-2-2025-05-08`, `sonic-2-2025-06-11` | en, de, es, fr, ja, ko, pt, zh                                                                    |
| `sonic-turbo` | `sonic-turbo-2025-06-04`                                         | en, de, es, fr, ja, ko, pt, zh, hi                                                                |

## API changes

These endpoints will be discontinued on June 1, 2026.

| Discontinued Endpoint                      | Replacement                                |
| ------------------------------------------ | ------------------------------------------ |
| Voice Embedding: `POST /voices/clone/clip` | [Clone Voice](/api-reference/voices/clone) |
| Mix Voices: `POST /voices/mix`             | —                                          |
| Create Voice: `POST /voices`               | [Clone Voice](/api-reference/voices/clone) |

These endpoints will stop accepting voice embeddings on June 1, 2026.

| Endpoint with a breaking change       | Replacement                                            |
| ------------------------------------- | ------------------------------------------------------ |
| TTS (bytes): `POST /tts/bytes`        | [Voice IDs](/build-with-cartesia/tts-models/voice-ids) |
| TTS (SSE): `POST /tts/sse`            | [Voice IDs](/build-with-cartesia/tts-models/voice-ids) |
| TTS (WebSocket): `WSS /tts/websocket` | [Voice IDs](/build-with-cartesia/tts-models/voice-ids) |

You can test these API changes by setting your [Cartesia Version](/use-the-api/api-conventions#always-send-a-cartesia-version-header) to `2026-03-01`. We recommend upgrading your Cartesia Version on production traffic before June 1 to make sure nothing breaks.

### Moving off of deprecated endpoints

1. Change how you create voices — see [Migrating Voices](/build-with-cartesia/tts-models/migrating-voices).
2. Switch from voice embeddings to IDs — see [Voice IDs](/build-with-cartesia/tts-models/voice-ids).

## Full Checklist

1. Move off of [deprecated models / snapshots / languages](/build-with-cartesia/tts-models/api-changes#deprecated-models-and-languages) onto `sonic-3.5` or another stable model
2. Move off of [deprecated endpoints](/build-with-cartesia/tts-models/api-changes#api-changes) when creating voices
3. Use [Voice IDs](/build-with-cartesia/tts-models/voice-ids)
4. Check your deprecated model traffic on [play.cartesia.ai/deprecation/traffic](https://play.cartesia.ai/deprecation/traffic)
5. Make sure your voices are migrated on [play.cartesia.ai/deprecation/voices](https://play.cartesia.ai/deprecation/voices)
6. (Optional) Upgrade your [Cartesia Version](/use-the-api/api-conventions#always-send-a-cartesia-version-header) to `2026-03-01`

## Why are we doing this?

Since the launch of Sonic 3, we've made improvements across pacing, prosody, and naturalness; the vast majority of our customers have migrated to these models with great success. In order to increase our capacity, availability, and serving performance, we have to discontinue our oldest models.

Additionally, our newer models have evolved beyond voice embeddings in order to sound more natural. The parts of our API that accept voice embeddings cannot be made forward-compatible. Migrating to voice IDs will allow us to continue to improve both our models and your voices in tandem.

If you have questions, reach out to [support@cartesia.ai](mailto:support@cartesia.ai).