AssemblyAI Inc. · Tools

AssemblyAI

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At a glance

Price
Pricing on request
Vendor
AssemblyAI Inc.

Specifications & properties

Key decision factors

Pricing model
Freemium 1
Audio functions
  • Speech-to-text
1

Pricing

Free tier
Yes 1

Integration

API available
Yes 1
Streaming API
Yes 1

Compliance

SOC 2
Yes 1
Report data / suggest a correction

Metrics vs. the category

Supported languages
n/a
Latency (real-time audio)
n/a

Speech-to-text API platform for pre-recorded and real-time transcription (Universal models). Usage-based pricing per audio hour (Universal-2 at $0.15/hr) rather than monthly plans; new accounts get $50 in free credits.

Profile

AssemblyAI is a speech-to-text and audio-intelligence API for developers, turning recorded or streaming audio into transcripts, speaker labels, summaries and other structured data. It's built for engineering teams shipping voice AI products, such as call analytics, meeting-notes tools, and voice agents, rather than for end users looking for a consumer app. Pricing is entirely usage-based: pre-recorded transcription starts at $0.15/hour on the Universal-2 model, real-time streaming starts at $0.15/hour, and new accounts get $50 in free credit with no credit card required.

Who builds it

AssemblyAI is built by AssemblyAI, Inc., founded in 2017 by CEO Dylan Fox and backed by a $50M Series C round led by Accel (announced December 2023) with participation from Y Combinator alumni investors, Insight Partners and others. The core workflow: send an audio file or a WebSocket stream to the API with a chosen model, and AssemblyAI returns a transcript plus optional add-on outputs like speaker diarization, sentiment analysis, summarization or PII redaction, which developers pull into their own product through the REST API or the official Python and JavaScript/Node.js SDKs.

Core features

  • Pre-recorded speech-to-text via the Universal-3.5 Pro ($0.21/hr) and Universal-2 ($0.15/hr) models, the latter supporting 99 languages
  • Real-time streaming transcription (Universal-3.5 Pro Realtime, Universal-Streaming English/Multilingual) billed on connection duration, from $0.15 to $0.45/hour
  • Voice Agent API bundling speech-to-text, LLM reasoning, text-to-speech, turn detection and interruption handling in one connection, at $0.075/minute
  • Speech Understanding add-ons: speaker diarization, sentiment analysis, auto chapters, topic detection, summarization and entity detection, each priced per hour on top of the base transcription rate
  • Guardrails for PII audio/text redaction, profanity filtering and content moderation
  • LLM Gateway giving direct, billed-per-token access to OpenAI, Anthropic, Google and other model providers alongside transcripts

Pricing

  • Free: $50 in free credit on signup, no credit card required, capped at 5 new streams/minute
  • Pre-recorded transcription: from $0.15/hour (Universal-2) to $0.21/hour (Universal-3.5 Pro)
  • Streaming transcription: from $0.15/hour (Universal-Streaming) to $0.45/hour base (Universal-3.5 Pro Realtime)
  • Voice Agent API: $0.075/minute ($4.50/hour) all-inclusive
  • Add-ons such as diarization, redaction, translation and sentiment stack on top of the base rate, typically $0.01-$0.15/hour
  • There is no flat monthly plan; billing is entirely pay-as-you-go and scales with volume, so check AssemblyAI's pricing page for current per-hour rates

Who it's for

The $50 free credit is enough for developers to prototype a transcription or voice-agent feature before entering a card. Pay-as-you-go pricing suits startups and scale-ups building voice products, such as call centers, meeting tools, or media captioning, who want to pay for what they process rather than commit to a seat-based SaaS plan. Teams needing compliance features like PII redaction or content moderation, or wanting to pair different LLMs with the same voice pipeline, are the target audience for the add-on and LLM Gateway layers.

Frequently asked questions

What does AssemblyAI cost?

AssemblyAI is priced per hour of audio processed rather than as a flat subscription. Pre-recorded transcription starts at $0.15/hour on the Universal-2 model and $0.21/hour on the higher-accuracy Universal-3.5 Pro model, real-time streaming starts at $0.15/hour, and the Voice Agent API (speech-to-text, LLM and text-to-speech bundled) costs $0.075/minute. Optional add-ons like speaker diarization, PII redaction or sentiment analysis stack $0.01-$0.15/hour on top of the base rate, so check AssemblyAI's pricing page for the current full rate card.

Is AssemblyAI free?

There's no permanent free tier, but new accounts get $50 in free credit with no credit card required, enough to test transcription, streaming or the Voice Agent API before paying. After the credit is used, billing switches to the standard pay-as-you-go per-hour or per-minute rates.

What languages does AssemblyAI support?

Language coverage depends on the model. The Universal-2 model supports 99 languages, with accuracy grouped into tiers by word-error-rate for each, while the newer Universal-3.5 Pro model covers 18 languages including English, Spanish, French, German, Mandarin Chinese, Arabic, Hindi, Japanese and Portuguese, with automatic handling of regional dialects such as Mexican Spanish and Québécois French.

Does AssemblyAI have an API?

Yes, AssemblyAI is an API-first product: it offers a REST API for pre-recorded transcription, a WebSocket API for real-time streaming and Voice Agents, and official Python and JavaScript/Node.js SDKs. Its docs also expose an LLM Gateway endpoint for pairing transcripts with OpenAI, Anthropic, Google and other model providers in the same request flow.

Can I use AssemblyAI transcripts commercially?

Yes. Per AssemblyAI's Terms of Service, customers retain ownership of the Output (transcripts and derived data) and may use it commercially, though AssemblyAI notes Output may contain errors and prohibits presenting it as human-generated. AssemblyAI separately retains rights to use de-identified and usage data for model training and product improvement, so review the ToS if data-handling terms matter for your use case.

AssemblyAI vs Deepgram: how does pricing compare?

Both are usage-based speech-to-text APIs, but their published rates aren't directly comparable at face value since Deepgram prices per minute and AssemblyAI per hour. Deepgram's Nova-3 model starts around $0.0048/minute (roughly $0.29/hour) pay-as-you-go with a $200 signup credit, while AssemblyAI's Universal-2 model is $0.15/hour with a $50 signup credit, so Deepgram's headline per-hour rate is cheaper on paper, though real-world cost depends on which add-ons, such as diarization, redaction, or multilingual support, each project needs.