Best for
Best for developers who need accurate transcription, speech insights or voice agents behind a pay-as-you-go API.
- Small and mid-sized
- Enterprise
AI Voice & Speech Comparison
AssemblyAI vs. Vapi
At a glance
At a glance
Best for
Best for developers putting voice agents on real phone lines for support, lead qualification or scheduling.
- Small and mid-sized
- Enterprise
Cataleo does not name a winner. Both statements come from the vendors themselves.
Full Comparison
| Criterion | AssemblyAI | Vapi |
|---|---|---|
| Starting price | From $0.15 / hour of audio Pay-as-you-go, no subscription tiers. Pre-recorded speech-to-text is $0.15 / hour on Universal-2 and $0.21 / hour on Universal-3.5 Pro; streaming is $0.15 / hour on Universal-Streaming and $0.45 / hour on Universal-3.5 Pro Realtime; the Voice Agent API is $4.50 / hour, billed per second of connected conversation. Add-ons such as speaker diarization ($0.02 / hour) and medical mode ($0.15 / hour) are charged on top. | lower value From $0.05 / minute of calls Build plan, usage-based, plus $0.005 per SMS or chat message. Ten concurrent lines are included and further lines cost $10 / month each. Model provider costs for speech-to-text, the LLM and text-to-speech are passed through at cost, or nothing if you bring your own API keys. |
| Free trial | $50 in free credits, no credit card required, covering up to 185 hours of pre-recorded or 333 hours of streaming transcription | Not stated |
| Commercial use | Yes, usage-based | Yes, usage-based |
| Output | Transcripts, structured speech insights and live voice agent conversations | Voice agents for inbound and outbound phone calls, web voice, and SMS or chat |
| API | Yes, REST APIs and SDKs | Yes, REST API, CLI and SDKs |
| Voice cloning | No, the platform covers speech recognition and voice agents rather than voice creation | Not part of Vapi itself; voices come from connected providers such as ElevenLabs and Deepgram |
| Real-time use | Yes, streaming speech-to-text and a Voice Agent API, alongside batch transcription of pre-recorded files | Yes, live inbound and outbound phone and web conversations at an average latency under 500 ms |
| Languages | 99 languages for pre-recorded audio on Universal-2, 18 on Universal-3.5 Pro; six on Universal-Streaming Multilingual and 18 on Universal-3.5 Pro Realtime; translation across 100+ languages | Depends on the providers chosen for a given assistant: automatic language detection and code-switching with Deepgram (100+ languages), Google STT (125+) or Gladia (110+), while Azure, OpenAI Whisper, Speechmatics and Talkscriber run one language at a time; on the voice side Vapi's own voices cover 40+ languages, Azure 140+ and ElevenLabs 30+. The languages an assistant may use have to be listed in its system prompt |
| Speech-to-speech and dubbing | Yes, the Voice Agent API runs speech-to-speech conversations by orchestrating speech-to-text, an LLM and text-to-speech at one all-inclusive rate | Yes, a call runs as spoken conversation by chaining speech-to-text, a language model and text-to-speech, with natural turn-taking |
| Editing and controls | Speaker identification, diarization, custom formatting, key phrase extraction and guardrails for PII redaction, profanity filtering and content moderation | Assistants for a single prompt with tools, Squads for multi-assistant orchestration, tool calls into APIs and databases mid-conversation, plus testing and call observability |
| Consent and trust | SOC 2 Type 2, ISO 27001, PCI-DSS and a HIPAA BAA included at no premium; EU region available at identical US pricing for GDPR | SOC 2, HIPAA and PCI compliance with SSO, OAuth and role-based access control; HIPAA is a $2,000 / month add-on and zero data retention $1,000 / month on both plans |
| MCP-ready | Yes | Yes |
| Deployment | Cloud (SaaS), Browser-based | Cloud (SaaS), Browser-based |
| Support | Not stated | Email helpdesk, Community forum |
| Onboarding | Documentation and knowledge base | Documentation and knowledge base |
| Company size | Small and mid-sized, Enterprise | Small and mid-sized, Enterprise |
| Integrations | Not stated | OpenAI, Anthropic, Groq, Deepgram, Gladia, ElevenLabs, Salesforce, HubSpot, Zapier, Slack, Google Workspace |
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The short version
Key Differences
- Starting price AssemblyAI From $0.15 / hour of audio Vapi From $0.05 / minute of calls
- Output AssemblyAI Transcripts, structured speech insights and live voice agent conversations Vapi Voice agents for inbound and outbound phone calls, web voice, and SMS or chat
- API AssemblyAI Yes, REST APIs and SDKs Vapi Yes, REST API, CLI and SDKs
- Voice cloning AssemblyAI No, the platform covers speech recognition and voice agents rather than voice creation Vapi Not part of Vapi itself; voices come from connected providers such as ElevenLabs and Deepgram
- Real-time use AssemblyAI Yes, streaming speech-to-text and a Voice Agent API, alongside batch transcription of pre-recorded files Vapi Yes, live inbound and outbound phone and web conversations at an average latency under 500 ms
Every line is one datapoint from the table above, picked automatically. Nothing here is written text.
The trade-offs
Strengths and Limitations
AssemblyAI
Strengths
- Pay-as-you-go with no subscription and $50 in free credits to start
- 99 languages for pre-recorded transcription on Universal-2
- Compliance certifications and an EU region at no price premium
- Official MCP server exposes transcription and transcript search to AI agents
Limitations
- A developer API, not a ready-made studio or editor
- No voice cloning or voice creation
- Speech Understanding add-ons are billed on top of the base rate, so cost stacks per request
- Streaming is billed for as long as the connection stays open, not for the audio sent, and multichannel files are billed per channel
- Universal-3.5 Pro covers 18 languages against 99 on the older Universal-2
Vapi
Strengths
- Per-minute pricing with model provider costs passed through at cost
- Bring your own provider keys and the pass-through drops to nothing
- Free choice of speech-to-text, model and voice provider across dozens of options
- Official MCP server lets external AI agents drive Vapi's APIs
Limitations
- HIPAA compliance and zero data retention are monthly add-ons rather than included
- Total cost depends on which model, transcription and voice providers you choose
- Concurrent lines beyond the first ten cost $10 per month each
- A platform to build on, not a finished call-centre product
Plans
Pricing
AssemblyAI
- Pay-as-you-go From $0.15 / hour No subscription. Pre-recorded transcription $0.15 / hour on Universal-2 and $0.21 / hour on Universal-3.5 Pro, streaming $0.15 / hour on Universal-Streaming and $0.45 / hour on Universal-3.5 Pro Realtime, Voice Agent API $4.50 / hour. Add-ons are billed on top: speaker diarization $0.02 / hour, medical mode $0.15 / hour, keyterms prompting $0.05 / hour on Universal-3.5 Pro and included on Universal-2. Free accounts get 5 new streams per minute, pay-as-you-go accounts 100.
- Custom Not stated Contact sales for custom rate limits, higher concurrency and volume discounts. HIPAA BAA, PCI-DSS, ISO 27001 and SOC 2 Type 2 compliance at no premium, and an EU region at identical US pricing.
Vapi
- Build $0.05 Per minute of calls, usage-based, plus $0.005 per SMS or chat message. Ten call concurrency included, additional lines $10 / month each. Model provider costs at cost. Community Discord and email support.
- Scale Not stated Annual contract with a fixed platform fee and committed volume, volume-based per-minute pricing on quote, enterprise features including SOC 2, HIPAA and PCI, a dedicated account team and a custom support SLA.
What users say
Review Scores · opens after launch
AssemblyAI
- Ease of use
- Not rated yet
- User interface
- Not rated yet
- Onboarding
- Not rated yet
- Support and service
- Not rated yet
- Value for money
- Not rated yet
- Features
- Not rated yet
No reviews yet. Be the first to review this tool. Every review is checked for fairness before it appears, and the vendor cannot have one removed.
Vapi
- Ease of use
- Not rated yet
- User interface
- Not rated yet
- Onboarding
- Not rated yet
- Support and service
- Not rated yet
- Value for money
- Not rated yet
- Features
- Not rated yet
No reviews yet. Be the first to review this tool. Every review is checked for fairness before it appears, and the vendor cannot have one removed.
Where this comes from
Where this comes from
AssemblyAI https://www.assemblyai.com · checked against the official source on 2026-08-30
Vapi https://vapi.ai · checked against the official source on 2026-08-30
This table lists factual criteria taken from information the vendors publish themselves. For how we put it together, see the methodology.