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ByteDance · Text to Speech

Seed Audio 1.0 API

ByteDance's Seed Audio 1.0 — prompt-directed audio creation: describe the voice, emotion, and sound staging in natural language. Up to 120s output, mp3/wav. Billed by audio duration ($0.003/second, estimated from input length).

about $0.316 per 1,000 characters · priced before it runs · no subscription

About ByteDance Seed Audio 1.0

Seed Audio 1.0 is a text-to-speech model from ByteDance that reads up to 3,000 characters per request aloud. It is billed on the seconds of audio it produces, about $0.316 per 1,000 characters of typical text. You can call it without an account, an API key or a subscription.

Use Seed Audio 1.0 for

  • Voice for agents and assistants that answer out loud
  • Narration for articles, courses and product videos
  • Accessibility: reading an app's own text aloud on demand

Seed Audio 1.0 specs

Endpoint
POST /api/v1/audio/speech
Price
about $0.316 per 1,000 characters
Longest input
3,000 characters per request
Billing basis
Seconds of audio produced

How to call Seed Audio 1.0

Pass bytedance/seed-audio-1.0 as the model field. The first request returns a 402 with the exact price; a signed retry runs it, and the client libraries fold the two into one call — how the payment works. Request and response shapes are in the docs.

curl -X POST https://blockrun.ai/api/v1/audio/speech \
  -H "Content-Type: application/json" \
  -d '{"model": "bytedance/seed-audio-1.0", "input": "Your order has shipped and arrives on Friday."}'

Seed Audio 1.0 or another speech model

Every speech model here takes the same request on the same endpoint, so trying another is a one-line change to the model field. The Text to Speech API page lists all of them side by side.

Seed Audio 1.0 API questions

How much does the Seed Audio 1.0 API cost?

About $0.316 per 1,000 characters, including the per-call transaction fee. The exact price is quoted in the 402 response before anything is generated, and you pay per request with no subscription.

Do I need an API key to use Seed Audio 1.0?

No. Each request carries its own payment, so an agent or script can call Seed Audio 1.0 with no account and no key. Teams that prefer one can use an API key with card or invoice billing instead.

How do I call Seed Audio 1.0?

Send a POST to /api/v1/audio/speech with "model": "bytedance/seed-audio-1.0". The request shape is shown above, and the same endpoint serves every speech model on the catalog, so switching models is a one-line change.

How long can the text be for Seed Audio 1.0?

Up to 3,000 characters per request. Longer text can be split across requests, each priced on its own.

Seed Audio 1.0 or another model — which should I use?

Compare it with ElevenLabs Flash v2.5 ($0.0535 per 1,000 characters), ElevenLabs Turbo v2.5 ($0.0535 per 1,000 characters), ElevenLabs Multilingual v2 ($0.106 per 1,000 characters) in the table above. They take the same request on the same endpoint, so you can try two on one prompt and keep the one you prefer.

Two ways to run this

Get an API key

Sign in, get a key, and call the same endpoints with usage billed to your account. For teams that want one invoice instead of one wallet.

Get an API key 

Or let your agent pay per call, in USDC

No account, no API key. Three steps, and the last one is the request this page is about.

  1. 01
    Point your agent at BlockRun

    Install ClawRouter, or add the BlockRun MCP server to Claude Code, Cursor, Codex or OpenClaw. Any OpenAI-compatible client works too — change the base URL, nothing else.

    curl -fsSL https://blockrun.ai/ClawRouter-update | bash
  2. 02
    Fund a wallet with USDC

    Send USDC to a wallet on Base, Solana or Arc. There is no account to create and no API key to issue: the wallet is the account, and it pays per call.

  3. 03
    Call Seed Audio 1.0

    The first call returns HTTP 402 with the exact price, your agent signs it, and the answer comes back. Payment settles on-chain; nothing is charged if the call fails.

    curl -X POST https://blockrun.ai/api/v1/audio/speech \
  -H "Content-Type: application/json" \
  -d '{"model": "bytedance/seed-audio-1.0", "input": "Your order has shipped and arrives on Friday."}'
ClawRouter setup →How paying per call works →

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