AssemblyAI

AssemblyAI is a speech AI platform that provides APIs to transcribe audio, understand speech context, and build voice agents.

AssemblyAI provides APIs and models that let developers transcribe speech to text and extract insights from voice data. The platform offers pre-recorded, real-time, and sync speech-to-text capabilities, along with a voice agent API and a speech understanding API. It supports features like speaker identification, PII redaction, content moderation, and LLM routing. The service is designed for developers and companies building voice-enabled products across various stacks. Users can try the API for free and transition to pay-as-you-go pricing without commitments.

AssemblyAI at a glance

Best for: Software engineer
Runs on: API
Pricing: Start free, pay-as-you-go after that with custom plans available.
Released: August 2018
Category: AI audio tool
Website: assemblyai.com

Key features

Pre-recorded Speech-to-Text API
Realtime Speech-to-Text API
Sync Speech-to-Text API
Voice Agent API
Speech Understanding API
PII redaction and content moderation
LLM Gateway routing

Use it for

Transcribing pre-recorded audio and video files
Streaming live audio transcripts in real time
Building production-ready voice agents
Extracting speaker ID, sentiment, and summaries

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WeNet — Achieves state-of-the-art results on public speech datasets.
Pipecat — Builds real-time voice and multimodal agents with frame-level control.
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walkai-talkai — Control AI coding agents remotely using any handheld walkie-talkie.
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Whisper ASR Webservice — Provides a REST API for multiple ASR engines including WhisperX and Faster Whisper.
sherpa-onnx — Runs complex audio AI tasks offline on local devices and embedded hardware.
Vision Agents — It enables building low-latency AI agents with support for any model.
Human or AI? — Identifies AI-generated voices in real time directly inside the browser.

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