AssemblyAI

Voice To Text

AssemblyAI is a developer-first speech intelligence platform. It provides speech-to-text (batch and streaming), speech understanding features (summarisation, PII redaction, topic detection), and a bundled Voice Agent API that combines STT, LLM routing, TTS, and turn detection over one WebSocket. It targets product teams building transcription, analytics, or voice agents without stitching multiple vendors.

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Features & details

Full overview from our catalog (read-only reference).

Category (short)

Voice To Text

Sponsored note

Target audience

Engineering teams building voice features, Startups wanting fast path to production voice agents, Products needing accurate STT with rich add-ons, Enterprises requiring HIPAA/SOC 2 on voice workflows, Less ideal for: non-technical users wanting a no-code call centre UI out of the box.

Best for

Pricing notes

Verified from official docs/pricing (July 2026): Product — Price Universal-3.5 Pro (async) — $0.21/hr Universal-3.5 Pro (streaming/sync) — $0.45/hr Universal-2 (async/streaming) — $0.15/hr Voice Agent API — $4.50/hr ($0.075/min) all-inclusive STT+LLM+TTS Medical Mode add-on — +$0.15/hr Speaker diarisation (async) — +$0.02/hr Keyterm prompting — +$0.05/hr Free tier: $50 credits (STT, Voice Agent, Speech Understanding; not LLM Gateway). Billing: Per second, pay-as-you-go. Enterprise: Custom volume pricing.

Pros & cons

Editorial notes to help compare fit before opening the vendor site.

Pros

Transparent per-hour/per-second billing, no minimum contract (self-serve)
Competitive async STT rates (U3.5 Pro async ~$0.21/hr per vendor blog, July 2026)
Voice Agent API reduces integration work vs DIY stacks
Strong documentation and model selection guidance
$50 free credits for new accounts (excludes LLM Gateway usage)
Failed transcripts not charged (vendor docs)

Cons

LLM Gateway billed separately
total voice agent cost adds up at scale
Streaming and sync STT priced higher than async
Add-ons stack quickly (diarisation, keyterms, medical mode)
Voice Agent API less flexible than best-of-breed STT + own LLM for tinkerers
Requires engineering resources to integrate

Review notes

Context from the listing review and editorial research.

Overall market reception: Strong among developers. Frequently compared favourably to Deepgram and OpenAI Whisper on price/features for production STT. Common praise: Accuracy, API quality, Voice Agent API time-to-production, documentation. Common criticisms: Cost at scale with add-ons, LLM Gateway complexity, streaming pricing vs async. Ratings: G2/Capterra scores not pulled in this pass; developer community reception generally positive.

Extended features

In-depth description and capability notes.

Universal models (U3.5 Pro, Universal-2) — Async and streaming STT with broad language support. Voice Agent API — All-in-one real-time voice stack at $4.50/hr (STT + LLM + TTS + orchestration). LLM Gateway — Route to Claude, GPT, Gemini, etc. with token-based billing separate from audio. Add-ons — Speaker diarisation, keyterm prompting, medical mode, auto chapters, summarisation. Integrations — Twilio, Telnyx, and voice-agent deployment docs. Compliance — HIPAA BAA, SOC 2, PCI for Voice Agent API (vendor claims).

Use cases

AssemblyAI fits engineering teams adding voice to products: call transcription, meeting notes, voice customer support, medical scribing (with Medical Mode), and sales call analytics. Choose the Voice Agent API when you want one vendor for the full spoken pipeline; choose raw STT when you bring your own LLM/TTS. Call centre transcription and QA Real-time voice agents for support and scheduling Podcast and media transcription pipelines Meeting note products Compliance-sensitive healthcare intake (verify BAA path) Content moderation and PII redaction on audio Sales call coaching and keyword spotting Developer prototypes with $50 free credits