Changelog

simba-english and simba-multilingual - the Simba 1.6 pair - are being withdrawn in two steps:

• From API version 2026-09-21 they are no longer selectable. Naming either returns 400 with the error code model_retired.
• On 2026-11-21 both models are switched off. From that date they are unreachable on every API version, including a workspace pinned below the retirement.

Requests that ask for MP3 without naming a bitrate now receive 128 kbps instead of 64 kbps. That is audio_format: "mp3" on POST /v1/audio/speech and POST /v1/audio/dialogue, and Accept: audio/mpeg on POST /v1/audio/stream and POST /v1/audio/stream/with-timestamps. The sample rate, channel count, duration and container are unchanged: 24 kHz mono MP3, as before.

output_format gains mp3_22050_160 and mp3_24000_160, the highest-fidelity mp3 the format can carry: 160 kbps is the ceiling at these sample rates, so there is no higher mp3 to ask for. A request for mp3_22050_192 or mp3_24000_192 was always encoded at 160 kbps, and the response now reports the mp3_*_160 it actually delivered rather than echoing the 192 back. Nothing about those two requests changes on the wire except the reported value, and no existing integration has to move.

Consent verification now checks who is speaking, not only what they said. A create whose consent_recording reads the phrase correctly but in a different voice from your sample is refused with 422 consent_speaker_mismatch and no voice is created.

This closes the gap the flow was always meant to close: the person consenting has to be the person being cloned, so permission relayed by somebody else - an account holder reading the phrase on a speaker’s behalf - does not pass.

Creating a cloned voice now requires proof that the speaker agreed to it, in place of the consent object you used to send.

The flow adds one call in front of your existing create. POST /v1/voices/consent-challenges with the speaker’s full_name returns a phrase and an id. Show the phrase to the speaker exactly as it comes back, record them reading it aloud, and send that recording as consent_recording with consent_challenge_id on POST /v1/voices. Speechify transcribes the recording, checks it against the phrase it issued, and keeps it as the consent record for that voice.

Text you send for synthesis is now screened before Speechify produces audio from it. A request whose content is not permitted returns 400 content_policy_violation with no audio, and is not billed. This applies to /v1/audio/speech, /v1/audio/stream, /v1/audio/stream/with-timestamps and /v1/audio/dialogue, and to an agent’s prompt and first_message when you create or update one.

Cloned (personal) voices now synthesize on simba-3.2 for workspaces enabled for it, with no per-voice step. The earlier per-voice-key approval is gone: enablement is per workspace, and once yours is on, every clone you own works there. Contact us to be enabled.

Nothing else changes. The request and response are identical to a stock-voice call, and simba-3.2 remains English only, so a cloned voice with a non-English locale still returns 400 — use simba-3.0 for those. GET /v1/voices names simba-3.2 on your cloned voices once your workspace is enabled, so drive a picker off each voice’s models array rather than assuming. Cloning on simba-3.0, simba-english and simba-multilingual is unchanged.

POST /v1/audio/speech, POST /v1/audio/stream and POST /v1/audio/stream/with-timestamps now resolve a request that omits model to simba-3.0 instead of the legacy simba-english. GET /v1/audio/models marks the change on its default flag.

Nothing you already send changes shape, and nothing that worked starts failing. A request that names a model explicitly is untouched - model: "simba-english" keeps getting Simba 1.6 English, and that model stays fully supported with nothing scheduled for removal.

GET /v1/audio/models now returns two new fields for each model:

• endpoints — the synthesis routes this model may be passed to. Passing a model to an endpoint its endpoints list omits returns 400.
• curated_voices — when true, only voices that explicitly name this model in their models array are accepted. When false, every catalogue voice works, including workspace clones.

The Free plan’s TTS rate limit no longer caps its burst bucket at the sustained rate. Previously Free was 1 request/second with a bucket capacity of 1, so a second request issued in the same second was rejected with 429. Free now gets a burst capacity of 10, so a normal opening burst of requests (a quickstart script, a first integration test) no longer trips the limiter.

Every header in Speechify’s public API surface now has one canonical, un-prefixed Speechify-* name (RFC 6648). The pre-2026 X--prefixed spellings are unaffected today - they’re still accepted on requests and still emitted on responses - and will keep working until 2027-07-24.

A new endpoint streams word-level speech marks alongside audio, so text highlighting, captions, and audio-text sync no longer need the batch POST /v1/audio/speech round trip. POST /v1/audio/stream is unchanged - same request body, still plain audio.

$
curl -N -X POST https://api.speechify.ai/v1/audio/stream/with-timestamps \
>
  -H "Authorization: Bearer $SPEECHIFY_API_KEY" \
>
  -H "Content-Type: application/json" \
>
  -d '{
>
    "input": "Hello world.",
>
    "voice_id": "oliver",

simba-3.0 is no longer English-only. It now officially supports English plus German, Spanish (Spain and Mexico), French, Italian and Brazilian Portuguese:

Nothing changes in your request shape. Keep passing model: "simba-3.0" and set the language parameter to the language of your input; when you omit language, the voice’s own locale decides. English and non-English are served by two separate trainings behind the scenes, but that routing is internal, so the model ID you pass never changes.

GET /v1/voices now accepts four optional query filters:

The API limits reference now lists the per-plan rate limits (sustained requests per second, plus a burst allowance on Agents) and concurrency limits (simultaneous in-flight requests) for every plan, across both the audio (TTS) and Agents surfaces. Limits apply per account, not per API key.

429 Too Many Requests responses are now self-describing:

simba-3.0 now accepts cloned and personal voices on POST /v1/audio/speech and POST /v1/audio/stream. Pass a cloned voice’s voice_id with model: "simba-3.0", the same way you would with simba-english. Zero-shot clones (from a 10-30 second sample) are supported self-serve; fine-tuned voices remain on simba-english and simba-multilingual (contact sales).

Cloned (personal) voices can now be synthesized on simba-3.2. Given the model’s quality bar, each cloned voice must first be reviewed and approved by Speechify — contact us to have a voice key approved for simba-3.2 — while we evaluate stronger safeguards. This is zero-shot cloning, gated only on that manual approval step.

simba-english and simba-multilingual continue to serve cloned voices self-serve, with no approval step and no change to existing integrations; simba-multilingual still speaks one cloned voice across 30+ languages. Once Speechify has approved a cloned voice key, pass it as voice_id with model: "simba-3.2".

GET /v1/audio/models returns the text-to-speech models you can pass as the model parameter, so you can populate a model picker at runtime instead of hardcoding the list.

1
{
2
  "models": [
3
    { "id": "simba-english", "name": "Simba English", "default": true, "recommended": false, "description": "English-only synthesis; the model used when a request omits `model`.", "languages": ["en"] },
4
    { "id": "simba-multilingual", "name": "Simba Multilingual", "default": false, "recommended": false, "description": "Synthesis across 30+ languages, including mixed-language input.", "languages": ["en", "fr-FR", "de-DE", "es-MX", "…"] },
5
    { "id": "simba-3.0", "name": "Simba 3.0", "default": false, "recommended": false, "description": "Earlier streaming-native model, English only. Superseded by simba-3.2.", "languages": ["en"] },
6
    { "id": "simba-3.2", "name": "Simba 3.2", "default": false, "recommended": true, "description": "Streaming-native model with the lowest time-to-first-byte and richest expressivity, English only today.", "languages": ["en"] }

simba-3.2 is now available on POST /v1/audio/speech and POST /v1/audio/stream via the model field. It is the go-forward Simba 3 model — streaming-native, with lower TTFB and richer expressivity than simba-3.0. We recommend simba-3.2 for new English integrations.

simba-3.2 serves from a curated voice allow-list. Pass one of its registered voice IDs as voice_id: beatrice_32, dominic_32, edmund_32, geffen_32, harper_32, hugh_32, imogen_32, wyatt_32.

The voice-gender enum value notSpecified is renamed not_specified so the gender vocabulary is consistent snake_case across the API. This affects the gender field on GET /v1/voices, GET /v1/voices/{voice_id}, and POST /v1/voices (request enum and response), and the male/female values are unchanged.

• Before (pin 2026-06-27 or earlier): the unspecified gender is notSpecified.
• After (2026-06-28+): the unspecified gender is not_specified.