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Assemblyai

Provides speech-to-text transcription and audio analysis using AI technology.

Our take: AssemblyAI offers a best-in-class API for converting audio and video to text, with a rich add-on layer covering diarization, summarization, sentiment analysis, entity detection, content moderation, and a real-time Voice Agent API.

Best forDevelopers
ReviewedPricing: Freemium
8.0 out of 105 criteria · see breakdown
Try AssemblyaiFree ($50 credits); from $0.15/hr
The bottom line

The go-to speech-to-text API for developers who need accuracy, a rich feature add-on stack, and transparent usage-based pricing.

Our score

Reviewed by the Conversion Gems editorial team. Hover a facet to focus it; click to pin.Tap a facet to focus it.

Community ratings

Shown for context only. Our score is independent.

G2
4.6 out of 5
120+ reviews

4.6 / 5 aggregate · across 1 source

Third-party ratings shown verbatim; aggregate weighted by review volume.

What it is, and why we rate it

One line each. Open a row for detail.

What it really isAssemblyAI — developer API platform for speech-to-text transcription and audio intelligence.
Our takeAssemblyAI offers a best-in-class API for converting audio and video to text, with a rich add-on layer covering diarization, summarization, sentiment analysis, entity detection, content moderation, and a real-time Voice Agent API.
The product is freemium: new accounts get $50 in free credits (no card required), then pay purely on usage. Pricing is usage-based per hour of audio, not a seat or subscription model.
Why we rate itAssemblyAI ranks among the top STT APIs for accuracy on English and multilingual audio.
The $50 free credit lets developers fully evaluate the platform before spending a cent. The add-on model is genuinely developer-friendly — teams only pay for the intelligence features they activate.
The catchCosts compound quickly when stacking add-ons (diarization + sentiment + summarization can push effective rates to $0.35–$0.50/hr).
Streaming sessions bill on wall-clock duration, not active speech, so idle time inflates costs. No flat-rate plan for predictable high-volume billing.

Best / not good for

Best for
  • Developers building transcription pipelines for audio/video content
  • Teams needing conversation intelligence (diarization, sentiment, summaries) via API
  • Voice agent and real-time speech application builders
Not good for
  • Non-technical users needing a UI-first transcription tool without coding
  • High-volume cost-sensitive workloads needing negotiated flat rates
  • Teams requiring fully on-premises or air-gapped deployment
Trade-offs

Friction report

Trade-offs to know before signing up.

  1. Time to value
    Fast — $50 credits activate on signup with no credit card; first transcription API call achievable within minutes using official SDKs.
  2. Scale breakpoint
    Add-on stacking at scale: running diarization plus multiple NLP features on thousands of hours/month requires careful cost modeling; enterprise contract recommended above ~500 hrs/month.
  3. Walled garden
    Moderate — transcripts and JSON outputs are fully portable, but real-time streaming and Voice Agent orchestration create operational dependency on AssemblyAI infrastructure.
Still a fit?
If none of these block you, start on the free plan.
Try Assemblyai

A look inside

Assemblyai product screenshot

Frequently Asked Questions

Does this speech-to-text API accurately transcribe multiple languages and accents?

The speech-to-text API converts audio into accurate text across multiple languages and accents using advanced recognition models.

Can Assemblyai transcribe audio with speaker diarization?

Assemblyai transcribes audio with speaker diarization, distinguishing different speakers and creating timestamped transcripts.

How does AssemblyAI help developers convert audio and video files to text using its speech-to-text API with features like speaker diarization and sentiment analysis?

AssemblyAI converts audio and video to text with advanced speech-to-text API features including speaker diarization, sentiment analysis, and high accuracy transcription.

How does this AI speech-to-text platform convert audio into accurate, searchable transcripts?

The AI speech-to-text platform converts audio into accurate, searchable transcripts for transcription and analysis purposes.

How does this AI platform help users transcribe, analyze, and extract insights from audio content?

AI audio tools transcribe recordings, extract insights, and generate structured content from spoken data.

Alternatives

  • Step up

    AssemblyAI Enterprise — for custom SLAs, volume discounts, and dedicated support.

  • Lighter alternative

    Deepgram Nova-3 — comparable usage-based STT pricing with strong real-time accuracy when NLP add-ons aren't needed.

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Conversion Gems independently reviews every tool.

Tags

#SpeechToTextAPI#Transcription

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