ThinnestAI vs Cartesia
Cartesia makes the fastest English TTS in the world. ThinnestAI is a full voice agent platform — and Cartesia is one of the TTS providers we support.
- Cartesia is fundamentally a TTS company with a thin agent SDK. ThinnestAI is a full voice agent platform that can use Cartesia as a BYOK TTS provider.
- Cartesia Sonic supports 42 languages including Hindi, but Indic coverage beyond Hindi is thin. ThinnestAI routes 22 Indian languages across the best provider per language.
- If you want fast English TTS and are building everything else yourself, Cartesia is excellent. If you want a complete voice platform for Bharat, ThinnestAI is the fit.
Pricing note
Cartesia uses credit-based pricing (15 credits/sec for Sonic TTS). Line voice agents are $0.05 per creation plus provider pass-through. It is a TTS-first product — a full voice agent stack built on Cartesia still requires you to add STT, LLM routing, flow editing, phone procurement and billing. ThinnestAI gives you all of that plus Cartesia as a BYOK TTS option.
Feature-by-feature comparison
| Feature | ThinnestAI | Cartesia |
|---|---|---|
| Product scope | Full platform (STT + LLM + TTS + phone + flows + billing) | TTS + thin agent SDK |
| Indian language coverage | 22 Indic languages via provider routing | Hindi included in 42-language model; other Indic is thin |
| Phone / SIP out of the box | Native (Twilio + Vobiz BYOK) | Not included — wire up Twilio + LiveKit yourself |
| English TTS speed / quality | Cartesia is available as BYOK | Sonic-3 — ~90ms TTFA, industry-leading |
| Voice cloning | Via BYOK providers (incl. Cartesia IVC/PVC) | Best-in-class voice cloning |
| INR billing / GST | Yes | No — USD credits |
You need the fastest English TTS
- You are building a product where TTS latency is the primary constraint.
- You need premium English voice cloning (IVC / PVC).
- You are building your own agent stack and only need a best-in-class TTS API.
- You are fine building everything else — STT, LLM routing, phone, flow editor — yourself.
You need a complete voice platform for Bharat
- You want STT, LLM, TTS, phone, flow editor and billing in one managed platform.
- You want 22 Indian languages supported via opinionated provider routing.
- You want INR billing and GST invoices.
- You can still use Cartesia as your TTS provider inside ThinnestAI — it's a BYOK option, not a competitor.
Frequently asked questions
Is ThinnestAI a competitor to Cartesia?
+
No. Cartesia is a TTS provider. ThinnestAI is a voice agent platform that treats Cartesia as one of several BYOK TTS options. You can build an agent in ThinnestAI that uses Cartesia Sonic for English and a different provider for Indian languages.
Does Cartesia Sonic support Hindi?
+
Yes — Hindi is included in the 42-language Sonic model. Quality is decent but not Indic-tuned. For production Hindi / Marathi / Tamil / Telugu deployments ThinnestAI routes to providers that specialize in those languages, which is usually a better fit.
Can I use Cartesia inside ThinnestAI?
+
Yes. Cartesia is a supported BYOK TTS provider in ThinnestAI. Bring your Cartesia API key and pick Sonic as the TTS for any agent.
When is Cartesia the right primary choice?
+
If you're an engineering team building your own voice stack and only need the fastest, most expressive English TTS API available. For anything beyond TTS (flow editing, phone, multi-provider routing, India ops) you'd be building it yourself.
Try ThinnestAI free
Start with welcome credits, no card required. Build your first Indian-language voice agent in under 5 minutes.