Assembly AI

AssemblyAI is a Voice AI infrastructure platform that provides developers with production-grade APIs for transcribing, understanding, and acting on speech. It serves engineering teams, startups, and enterprises building voice-enabled applications such as call analytics platforms, AI notetakers, voice agents, medical scribes, live captioning systems, and content repurposing tools.

Core Products

The platform offers a comprehensive suite of voice AI capabilities. The Pre-recorded Speech-to-Text API transcribes recorded audio and video files with models including Universal-3 Pro and Universal-2, supporting features like speaker diarization, multilingual transcription, medical mode, keyterms prompting, and custom formatting. The Real-time Speech-to-Text API delivers live streaming transcription over WebSocket connections for use cases such as live captioning, voice agent input, and real-time meeting assistance. The Voice Agent API provides a managed speech-to-speech agent stack over a single WebSocket connection, handling speech recognition, LLM reasoning, text-to-speech, turn detection, interruptions, and tool calling without requiring separate orchestration. The Speech Understanding API extracts structured insights from transcripts including entity detection, sentiment analysis, content moderation, topic detection, and translation across 100+ languages. The Guardrails product provides PII redaction (both text and audio), profanity filtering, and content moderation to protect sensitive content. The LLM Gateway offers a unified endpoint for 25+ language models from providers including OpenAI, Anthropic, Google, Alibaba Qwen, and Moonshot Kimi through a single API key.

Deployment Options

AssemblyAI provides two deployment models. AssemblyAI Cloud is a fully managed infrastructure with automatic scaling, available in both US and EU regions at the same price point. Self-Hosted Voice AI allows organizations to run AssemblyAI models on their own infrastructure for data sovereignty and control. The EU region endpoint ensures data remains within the European Union for GDPR compliance.

Key Capabilities

AssemblyAI's speech recognition models offer industry-leading accuracy benchmarks. The Universal-3 Pro model supports prompting for domain-specific vocabulary and code-switching between languages. The platform handles multichannel audio transcription billed per channel, supports automatic language detection for 99+ languages, and provides word-level timestamps and confidence scores by default. Speaker diarization is available in both pre-recorded and streaming modes, with Universal-3 Pro Streaming offering real-time inline diarization. Medical Mode improves transcription accuracy for clinical and medical terminology across English, Spanish, German, and French.

Integrations

The platform integrates with telephony tools (Twilio, Telnyx, Amazon Connect, Genesys Cloud), meeting platforms (Zoom with Recall.ai), voice agent orchestrators (LiveKit, Pipecat), no-code automation tools (Zapier, Make, n8n, Power Automate, Activepieces), AI frameworks (LangChain, Haystack, Semantic Kernel), and front-end frameworks. Official SDKs are available for Python, JavaScript/TypeScript, and community SDKs exist for additional languages.

Pricing

AssemblyAI offers a freemium model with $50 in free credits on signup with no credit card required. Pay-as-you-go pricing starts at $0.15 per hour for Universal-2 pre-recorded transcription and $0.21 per hour for Universal-3 Pro. Streaming transcription starts at $0.15 per hour for Universal-Streaming and $0.45 per hour for Universal-3 Pro Streaming. The Voice Agent API is priced at $4.50 per hour all-inclusive. Speech Understanding add-ons and LLM Gateway token pricing apply on top of base rates. HIPAA BAA is available without premium pricing, and the Voice Agent API is PCI-DSS certified. Enterprise volume discounts and custom concurrency limits are available.

Security and Compliance

AssemblyAI holds ISO 27001 certification, SOC 2 Type 2 attestation, and complies with GDPR. HIPAA Business Associate Agreements are available and can be signed without a sales call at no additional cost. Data encryption is applied at rest and in transit, and customers can opt out of data sharing for model improvement.