Changelog

simba-3.0 is now available on POST /v1/audio/speech and POST /v1/audio/stream via the model field. It’s the new streaming-native voice model with lower TTFB and richer expressivity, including direct support for per-voice speaking-rate and ADV (Arousal, Dominance, Valence) emotion controls inherited from the voice catalog.

1
{
2
  "input": "Hello, world!",
3
  "voice_id": "george",
4
  "model": "simba-3.0"
5
}

Currently English only — multilingual coming soon

simba-3.0 currently supports English voices only. Requests with a non-English voice return 400 with the rejected locale called out in the message. Multilingual support is coming soon; the model name stays simba-3.0 across that change, so no migration is required.

For non-English voices today, continue to use simba-multilingual.

New API Domain: api.speechify.ai

The Speechify API is now available at https://api.speechify.ai.

What Changed

• New base URL: https://api.speechify.ai
• New console URL: https://console.speechify.ai
• New docs URL: https://docs.speechify.ai

Migration

No action is required. The previous domains (api.sws.speechify.com, console.sws.speechify.com, docs.sws.speechify.com) continue to work and are not being deprecated.

Updated SDKs default to the new base URL. If you’ve hardcoded api.sws.speechify.com in your integration, it will continue to work.

API: Concurrency Limits for TTS Endpoints

We’ve introduced concurrency limits to prevent abuse and ensure fair usage across all users. These limits restrict the number of simultaneous in-flight text-to-speech requests per user.

Concurrency Limits

What This Means

• Free users are limited to 1 concurrent in-flight TTS request at a time
• Paid users can have up to 15 concurrent in-flight TTS requests
• Concurrency limits are enforced per user account, not per API key
• When the limit is exceeded, you’ll receive a 429 Too Many Requests response with a Retry-After header

Affected Endpoints

• POST /v1/audio/speech
• POST /v1/audio/stream

API: Differentiated Rate Limits for Free and Paid Users

We’ve introduced differentiated rate limiting based on user plan type to ensure fair usage and optimal performance for all users.

Rate Limits

What This Means

• Free users are now subject to a lower rate limit of 1 request per second
• Paid users continue to enjoy the standard rate limit of 20 requests per second
• When rate limited, responses include a Retry-After header indicating when to retry

Affected Endpoints

• POST /v1/audio/speech
• POST /v1/audio/stream

SDK: New Typescript SDK

We’ve published a new Typescript SDK. Try it out:

$
npm install @speechify/api

Together with the release, the old @speechify/api-sdk package is now deprecated.

Migrating from @speechify/api-sdk

Quick Start Guide

$
npm install @speechify/api

1
import { SpeechifyClient } from "@speechify/api";
2
3
// API Key can also be set as an environment variable SPEECHIFY_API_KEY
4
const client = new SpeechifyClient({ apiKey: "your-api-key" });

1
const voices = await client.tts.voices.list();

1
const result = await client.tts.audio.speech({
2
  voiceId: voices[0].id,
3
  input: "Hello, world!",
4
});

1
const audioData = result.audioData;
2
const audioBuffer = Buffer.from(audioData, "base64");
3
4
// Write the binary data to a file
5
fs.writeFileSync("speech.mp3", audioBuffer);

API: Deprecated POST /v1/auth/token endpoint

The POST /v1/auth/token endpoint is now deprecated. We will only support API Key authentication moving forward.

We’ve added a new option to the API to normalize the text. If enabled, it will transform numbers, dates, etc. into words. For example, “55” is normalized into “fifty five”. This can increase latency due to additional processing required for text normalization.

API: Loudness Normalization Update

Previously, the loudness normalization was enabled by default. Now it’s disabled by default as we believe, together with our internal model improvements, it will improve the overall quality of the audio.

SDK: Python

We’ve released a new Python SDK. Checkout the repository for more information.