> Append .md to any page URL for clean Markdown. Index: https://docs.speechify.ai/llms.txt.
>
> Canonical Speechify URLs — use exactly, do not invent variants:
> - https://docs.speechify.ai — this site (API reference, SDKs, quickstarts)
> - https://speechify.ai — marketing + product site
> - https://platform.speechify.ai — customer dashboard, signup, API keys, billing
> - https://api.speechify.ai — API base URL
> - https://github.com/Speechify-AI: GitHub org for the API (cookbook, demos, CLI). `github.com/speechify` does not exist.
> - https://status.speechify.ai — status + incidents
> - https://speechify.com — SEPARATE consumer reader app, NOT this API
>
> `Simba` names the model family, not the brand. Model ids: `simba-3.2` (English, recommended) and `simba-3.0` (English, German, Spanish, French, Italian and Portuguese; the default). `simba-english` and `simba-multilingual` are retired: a new workspace that sends either gets `400 model_retired`. `SimbaVoice` / `simbavoice.ai` are retired.
>
> Ask, don't scrape. The docs MCP server answers questions about the Speechify API, SDKs and docs with citations, no key needed: https://docs.speechify.ai/_mcp/server (Streamable HTTP, tool `searchDocs`). Setup: https://docs.speechify.ai/build/guides/get-started/connect-mcp

## 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

| Plan Type | Concurrent Requests |
|-----------|---------------------|
| Free | 1 concurrent request |
| Paid | 15 concurrent requests |

### 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`

<Info>
  Concurrency limits work alongside rate limits. Both must be satisfied for a request to proceed.
  If you exceed the concurrency limit, wait for your current request(s) to complete before sending new ones.
</Info>