Rev AI

Free tier

The world's most accurate speech-to-text API for developers, built for speed and global scale.

Free tier available·Technical·Powered by Rev AI (proprietary models trained on 7M+ hours of human-verified speech data)·API available

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Key strengths

Industry-leading Word Error Rate (WER) across diverse accents, genders, and nationalitiesSupports 57+ languages with context-aware translationHIPAA, SOC II, GDPR, and PCI compliant with 99.99% uptimeBoth async (pre-recorded) and streaming (real-time) speech-to-text APIsAI Insights layer: sentiment analysis, topic extraction, summarization, and language identification

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San Francisco, USA

Founded 2010

Self-hostable

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Real-time captioning pipelines — Stream audio over WebSocket to generate live captions for video conferencing or broadcast applications with sub-second latency.
Media indexing & search — Use forced alignment and word-level timestamps to make large audio/video archives fully searchable by content.
Voice analytics platforms — Chain the Speech-to-Text API with Sentiment Analysis and Topic Extraction APIs to analyze call center recordings or podcast content programmatically.
Multilingual NLP pipelines — Leverage Language Identification API to auto-detect language before routing audio to the correct downstream processing model.
Compliance & records management — Transcribe and archive sensitive audio (HIPAA/SOC II compliant) in healthcare, legal, or financial applications deployed on-premises.
Custom vocabulary integration — Register domain-specific terminology (medical, legal, technical) via custom vocabulary IDs to significantly reduce WER for specialized corpora.