AssemblyAI

AssemblyAI provides AI models that convert speech to text with industry-leading accuracy and the lowest word error rates available. Their platform offers Core Transcription for processing audio and video files, Streaming Speech-to-Text for real-time applications with ultra-low latency, and Speech Understanding capabilities including speaker diarization, sentiment analysis, summarization, and PII redaction.

Built for developers, AssemblyAI processes over 40 terabytes of audio daily and handles 600M+ inference calls monthly. Their Universal model family supports multilingual transcription with automatic language detection, while specialized features like automatic text formatting and alphanumeric recognition ensure clean, usable outputs.

AssemblyAI serves Fortune 500 companies, startups, and developers across telephony, video conferencing, media, contact centers, and healthcare. Their API-first approach, comprehensive documentation, and pay-as-you-use pricing make it straightforward to integrate speech AI into any application.

Vapi and and AssemblyAI combine to deliver high-performance voice AI applications. AssemblyAI's streaming speech-to-text integrates with Vapi's voice AI platform to provide real-time transcription with precise end-of-turn detection, enabling natural conversational experiences in voice agents.

The integration allows Vapi developers to leverage AssemblyAI's accuracy advantages—up to 30% fewer hallucinations than competitors and transcription quality preferred by 73% of end users in evaluations. This accuracy translates directly to better voice agent performance, as downstream intent recognition and response generation depend on reliable speech-to-text.

For applications requiring post-call analysis, AssemblyAI's Speech Understanding features extract actionable insights from voice interactions built on Vapi. Speaker diarization identifies participants, sentiment analysis tracks emotional dynamics, and summarization captures key points—all through a unified API. Together, Vapi and AssemblyAI enable developers to build voice applications that understand speech accurately and scale to millions of conversations.