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TTS-1

OpenAI Speech synthesisStreaming
Input$15/M
Context4K

Provider list prices: no platform markup, pay-as-you-go. These are official list prices. Logged-in customers may see effective prices including workspace discounts on /console/pricing.

Use TTS-1 in 30 seconds

OpenAI-compatible: swap the base_url, keep your SDK. POST /v1/chat/completions

from openai import OpenAI

client = OpenAI(
    base_url="https://synthorai.io/v1",
    api_key="sk-syn-...",
)

resp = client.chat.completions.create(
    model="tts-1",
    messages=[{"role": "user", "content": "Summarize this diff"}],
)
print(resp.choices[0].message.content)

Specs & limits

Audio

Languages
Generally follows the Whisper model’s language support: Afrikaans, Arabic, Armenian, Azerbaijani, Belarusian, Bosnian, Bulgarian, Catalan, Chinese, Croatian, Czech, Danish, Dutch, English, Estonian, Finnish, French, Galician, German, Greek, Hebrew, Hindi, Hungarian, Icelandic, Indonesian, Italian, Japanese, Kannada, Kazakh, Korean, Latvian, Lithuanian, Macedonian, Malay, Marathi, Maori, Nepali, Norwegian, Persian, Polish, Portuguese, Romanian, Russian, Serbian, Slovak, Slovenian, Spanish, Swahili, Swedish, Tagalog, Tamil, Thai, Turkish, Ukrainian, Urdu, Vietnamese and Welsh, despite voices being optimized for English
Audio limits
  • Speech generation endpoint (v1/audio/speech) only, with Chat Completions, Responses, Realtime, Batch and Fine-tuning all listed as not supported
  • input text is capped at 4096 characters
  • output mp3 (default), opus, aac, flac, wav or pcm (raw 24 kHz 16-bit signed little-endian samples)
  • realtime playback via chunked transfer encoding

Realtime

Voices
alloy, ash, coral, echo, fable, onyx, nova, sage and shimmer, a smaller set than the full 13-voice TTS list, and voices are currently optimized for English.

Model

Modalities
text → audio

Text-to-speech model optimized for speed: OpenAI documents tts-1 as the lower-latency, lower-quality option next to tts-1-hd. The instructions parameter that steers accent, emotion, intonation and tone on gpt-4o-mini-tts does not work with tts-1 or tts-1-hd.

per OpenAI official docs ↗

About TTS-1

Optimized for speed and realtime text-to-speech use cases
Lower latency at lower quality than tts-1-hd
No instructions parameter and no sse stream format

TTS-1 is OpenAI's text-to-speech model optimized for speed.

  • Its model page describes it as converting text to natural sounding spoken text and as tuned for realtime text-to-speech use cases, and the text-to-speech guide draws the family line plainly: tts-1 provides lower latency, but at a lower quality than tts-1-hd.
  • It is a single-purpose model, supported only on the Audio API speech endpoint and on no other route, taking text in and returning audio, priced at $15 per million characters.
  • Nine voices are available to it, a smaller set than the thirteen the Speech endpoint offers in total: alloy, ash, coral, echo, fable, onyx, nova, sage, and shimmer.
  • Output can be MP3 by default, or Opus, AAC, FLAC, WAV, or raw 24 kHz PCM, and OpenAI recommends WAV or PCM for the fastest response; speech rate is adjustable from 0.25 to 4.0, with 1.0 the default, and audio can be streamed with chunked transfer encoding so playback begins before the full file exists.
  • Two limits distinguish this generation from the newer one and will break copied code: the instructions parameter that steers accent, emotion, and delivery does not work on tts-1 or tts-1-hd, and the sse stream format is unsupported here.
  • Language coverage generally follows Whisper's list of more than fifty languages, though the voices themselves are optimized for English, and OpenAI's usage policies require telling end users that the voice is AI-generated.
  • Synthorai serves TTS-1 through its OpenAI-compatible /v1/audio/speech endpoint, so existing speech clients work unmodified.

FAQ

Is the TTS-1 API free to try?

Yes: new accounts get 10 trial calls and up to $1 in free credit, no card required. At $15/M input tokens, that credit alone covers roughly 16 requests of ~4K tokens against TTS-1.

What is TTS-1 best at?

Optimized for speed and realtime text-to-speech use cases; lower latency at lower quality than tts-1-hd; no instructions parameter and no sse stream format. See the About section for the full picture from the vendor's own release notes.

How much does TTS-1 cost?

TTS-1 costs $15 per million input tokens and $0 per million output tokens on Synthorai. That is the provider's list price, with no platform markup.

Does TTS-1 support prompt caching?

TTS-1 has no cache-read discount on Synthorai today. Prompt caching still applies to other models on the gateway; see the pricing table for cache-enabled alternatives. Provider caching comparison →

How do I get access to TTS-1?

Point your existing OpenAI SDK at base_url="https://synthorai.io/v1", set model="tts-1", and you're done. One API key covers every model on the gateway.

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