Production-grade speech-to-text API with Universal-3 Pro model, real-time streaming, and audio intelligence features for voice AI applications.
Speech-to-text API that converts audio files and real-time streams to text with speaker identification and sentiment analysis.
AssemblyAI provides speech-to-text APIs that actually work in production. Their Universal-3 Pro model charges $0.21 per hour for async transcription and $0.45 for real-time streaming — competitively priced against major cloud providers like Google and AWS. The platform includes $50 in free credits (roughly 235 hours of async transcription), making it accessible for prototyping before committing to production usage. Audio intelligence features like speaker diarization, sentiment analysis, and PII redaction are available as add-ons, and the LeMUR framework enables LLM-powered querying of transcripts directly through the API.
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AssemblyAI receives strong reviews for transcription accuracy and developer experience, with users particularly praising the comprehensive audio intelligence features and responsive support team. Common criticisms focus on costs at high volume and variable non-English accuracy.
Production-grade speech-to-text model at $0.21/hour async and $0.45/hour real-time, supporting 99+ languages with automatic detection. Consistently ranks in the top tier of the Open ASR Leaderboard for English conversational audio with 5-8% word error rates.
WebSocket-based streaming transcription with sub-300ms end-to-end latency, delivering both partial predictions (real-time guesses) and confident final results. This dual-output architecture is what makes conversational voice agents feel responsive during natural dialogue.
Bundled speaker diarization, sentiment analysis, PII redaction, entity detection, auto-chapters, and content moderation in a single API call. Speaker diarization identifies who spoke when across multi-person conversations. PII redaction automatically removes sensitive data like SSNs and credit card numbers.
Natural language querying of transcripts using Claude and other frontier LLMs, accessed through the same API as transcription. Ask 'What action items were discussed?' or 'Summarize the customer's complaints' and receive structured responses without building a separate LLM pipeline.
SOC 2 Type II certification, HIPAA compliance with signed BAAs, and EU data residency for GDPR workflows. Configurable retention policies including zero-retention processing where audio and transcripts are deleted immediately after processing completes.
$50 in free credits
$0.21/hour async, $0.45/hour streaming
Custom pricing
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AssemblyAI continues iterating on the Universal-3 Pro model with ongoing accuracy improvements on phone-call audio and expanded language coverage. LeMUR framework has expanded LLM provider support, and the platform has rolled out enhanced enterprise security controls and EU data residency options.
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