AssemblyAI

AssemblyAI builds AI models to transcribe and understand speech, paired with infrastructure built to run them. Its homepage calls them industry leading voice models and reports the scale behind that claim: more than 120 million conversations per week, more than 2 billion API calls a month, and 94 percent plus accuracy, with the company ranked first by independent benchmarks it publishes for voice agent name and number errors, speaker diarization, and text to speech word errors against other named providers. The platform is organized into inference, models, APIs, solutions, and configurable modes, so a team can adopt a single endpoint or the full stack. The model lineup shows the range. Universal-3.6 Pro is described as its most accurate speech to text model for recorded audio, Universal-3.6 Pro Realtime is the matching model for voice agents in real time, and AssemblyAI-TTS-1 is a new text to speech model built for voice agents and trained on millions of real phone calls. Inference runs two ways: a managed Voice AI Cloud with unlimited concurrency for production traffic, or self hosted deployment in the customer's own VPC or on premise, with full control of their data. That deployment choice is a central part of the pitch for teams with strict data requirements. The API surface covers the full job around a transcript. Pre-recorded, realtime, and sync speech to text endpoints handle files, streams, and short clips, with speaker labels and formatting; a Speech Understanding API adds summaries, sentiment, and entities built on transcripts; Guardrails detects and redacts PII and unsafe content in voice data; and separate endpoints cover natural, low latency text to speech, an LLM Gateway for models that perform best on voice tasks, and dictation anywhere users type. Named solutions include voice agents, meeting notetakers, agent assist on live calls, medical transcription, dictation, and AI scribes, with modes tuned for medical and veterinary vocabulary and a legal mode marked as coming soon. AssemblyAI suits builders who need accurate transcription first, with understanding, safety, and speech generation layered on the same platform.