What is AssemblyAI?
AssemblyAI is a Voice AI platform for developers. It offers pre-recorded and real-time speech-to-text APIs, plus tools to understand audio beyond words. You can extract speaker IDs, sentiment, chapters, and summaries from a single call. It also provides a Voice Agent API and an LLM Gateway for routing between models.
You start by signing up for free and getting an API key. Then you send audio through their REST or streaming APIs, or use their Python SDK. For real-time use, you connect a microphone stream and get transcripts as they happen. The playground lets you test models without writing code.
It suits developers building voice-enabled products, from call centers to apps. The site mentions 99 languages, enterprise-grade uptime, and processing 2 million hours of audio daily. Pricing scales from your first 100 hours to 400,000 hours a month, with no concurrency limits or forced commitments.
AssemblyAI features
- Pre-recorded Speech-to-Text: Get clean transcripts in 99 languages with industry-leading accuracy and natural language prompting.
- Realtime Speech-to-Text: Stream transcripts live with async-level accuracy, so your agent responds fast without mishearing.
- Speech Understanding API: Extract speaker ID, sentiment, chapters, and summaries from a single API call.
- Voice Agent API: Build production-ready voice agents with built-in turn detection and interruption handling.
- Guardrails: Redact PII and moderate content inline on audio and transcripts, keeping sensitive data out of logs.
What you can do with AssemblyAI
- Transcribe customer support calls and extract sentiment for quality analysis.
- Build a real-time voice assistant that responds to user speech without delay.
- Generate meeting summaries and chapters from recorded audio automatically.
- Redact personal information from audio transcripts before storing them.
How to get started with AssemblyAI
- Sign up for a free account on AssemblyAI's website to get your API key.
- Use the playground to test transcription with your own voice or sample audio.
- Integrate the API into your app using the Python SDK or REST endpoints.
Tips for better results with AssemblyAI
- Start with the playground to test Universal-3.5 Pro on your own audio before writing code, so you can verify accuracy and settings without burning API credits.
- Use the Speech Understanding API in a single call to pull speaker IDs, sentiment, chapters, and summaries together, saving time and reducing request overhead.
- For real-time projects, connect a microphone stream through AssemblyAI's Python SDK and test with continuous partials to see how quickly transcripts update during live speech.
- Redact PII inline with guardrails before storing transcripts, ensuring sensitive data never reaches your logs and simplifying compliance for production use.
AssemblyAI pricing
AssemblyAI has a free way to start, with paid plans for heavier use. Check assemblyai.com for current limits and prices.
What to check before you rely on AssemblyAI
- Check the pricing page for exact costs per hour beyond the free tier, since the site mentions scaling but does not list specific rates.
- Verify which languages and models are included in your plan, as the site claims 99 languages but does not state whether all are available on free access.
- Confirm data handling and retention policies before sending sensitive audio, since the site does not explicitly state how long audio or transcripts are stored.
Who AssemblyAI is for
AssemblyAI suits developers, voice AI builders and product teams. If that is not you, the AI transcription tools below may fit better.
Similar tools compared with AssemblyAI
| Tool | What it is | Pricing |
|---|---|---|
| AssemblyAI | Voice AI infrastructure for builders | Freemium |
| Otter.ai | AI meeting notetaker and transcription tool | Freemium |
| Fireflies.ai | AI meeting assistant for transcription and notes | Freemium |
| Fathom | AI notetaker for online meetings | Freemium |
| Turboscribe | Unlimited audio and video transcription | Freemium |
AssemblyAI FAQ
What does AssemblyAI do?
AssemblyAI provides APIs for speech-to-text, speech understanding, and voice agents. You can transcribe audio, extract insights like sentiment and chapters, and build real-time voice interactions.
Is AssemblyAI free to use?
The website offers a free sign-up, but it doesn't specify exact free limits or paid plan details. You can check the pricing page for current tiers and usage-based costs.
Who is AssemblyAI for?
It's for developers and builders who want to add voice AI to their products. The site says it's trusted by millions of developers and scales from MVP to production.
What languages does AssemblyAI support?
The pre-recorded speech-to-text API supports 99 languages. The realtime API also has a multilingual streaming option, though the site doesn't list all supported languages.
What can AssemblyAI export or connect to?
AssemblyAI provides REST and streaming APIs, plus a Python SDK, so you can send transcripts or analysis results to your own systems. The website does not list specific integrations like Zapier or Slack, so check the documentation or contact support for details on connecting to other tools.
Does AssemblyAI work on mobile devices or desktop?
AssemblyAI runs as a cloud API, so it works on any device that can send audio over the internet, including mobile and desktop. You can use its Python SDK or REST API from your app or server. The website does not mention a dedicated mobile app, so you would build your own interface.
What does the free plan of AssemblyAI include?
AssemblyAI is freemium, and you can sign up for free to get an API key. The website mentions your first 100 hours of audio processing, but it does not specify exactly what features are included in the free tier. Check the pricing page for current limits and what is available without payment.
