Directory / Voice AI / AssemblyAI
AssemblyAI
Voice AI platform with speech-to-text (pre-recorded and realtime), speech understanding, an LLM gateway and now text-to-speech — models, APIs and infrastructure to build voice into any product, including voice agents.
💲 Free tier, no card (up to 185 hrs pre-recorded and 333 hrs streaming transcription); then pay-as-you-go: Universal-2 $0.15/hr, Universal-3.5 Pro $0.21/hr, Universal-3.6 Pro Realtime $0.45/hr; AssemblyAI-TTS-1 $15 per 1M characters. Volume pricing via sales. Source: assemblyai.com (checked Oct 31, 2026).
Pros & cons
👍 Pros
- STT, realtime STT and TTS from one API for voice agents
- ~90 ms time to first audio, unlimited concurrency with no contract
- 4,000+ voices and instant voice cloning; LiveKit and Pipecat reference agents
👎 Cons
- TTS covers six languages at launch
- No pro voice cloning, pronunciation dictionaries or emotion tags yet
Latest release
AssemblyAI-TTS-1
First text-to-speech model, now GA and built for voice agents on live calls: streams audio in ~90 ms over WebSocket/HTTP (plus an OpenAI-compatible endpoint), English, Spanish, French, German, Italian and Portuguese, 4,000+ voices, instant cloning and word-level timestamps at $15 per 1M characters. Source ↗
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