In short
How they differ.
Worked out from the makers' own pages, read Oct 20, 2026. Prices change; check before you pay.
- Both have a free plan.
- Cartesia's cheapest paid plan is cheaper: $5 a month against $20.
- OpenAI speech models also has a phone app.
Side by side
The details.
| Cartesia | OpenAI speech models | |
|---|---|---|
| Made by | Cartesia · US | OpenAI · US |
| What it says it is | “Architecting AI that learns and interacts like humans.” | “The Audio API provides a speech endpoint based on our GPT-4o mini TTS (text-to-speech) model.” |
| Free plan | Yes20K credits/month (~27 minutes TTS); no commercial-use license; no instant voice cloning | YesChatGPT Free: 'Limited voice chats'; API is paid per token |
| Plans | Pro: $5 a monthStartup: $49 a monthScale: $299 a monthEnterprise: not in US$ | API gpt-realtime-2.1 (audio): not in US$API gpt-realtime-2.1-mini (audio): not in US$ChatGPT Plus: $20 a monthChatGPT Pro: $200 a month |
| Runs on | web, API | API, web, iOS, Android |
| Latest update | — | — |
| Its terms | — | “As between you and OpenAI, and to the extent permitted by applicable law, you (a) retain your ownership rights in Input and (b) own the Output.”Who owns what you make · OpenAI Terms of Use |
| Disputes | None on file | None on file |
| Sources | Prices, Oct 20, 2026 · Description · company-reported | Prices, Oct 20, 2026 · Description · company-reported |
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