AssemblyAI vs Cartesia
AssemblyAI and Cartesia are both audio AI tools, tracked here on price, platforms, integrations, and capabilities. Every figure below is read from the vendor's own pages and dated. No score and no winner: the facts do the picking.
AssemblyAI
Voice AI infrastructure for builders
AssemblyAI delivers production-ready Voice AI models, including pre-recorded and real-time streaming speech-to-text, speaker diarization, and voice agent APIs. It provides advanced models like Universal-3.5 Pro, supporting multiple languages and specialized medical transcription modes.
Cartesia
Real-time speech synthesis, transcription, and voice agent platform
Cartesia provides real-time voice intelligence powered by state space models, featuring Sonic-3.6 for text-to-speech and Ink-2 for transcription. Developers can build voice agents through Managed Agents or deploy custom implementations across cloud, on-premise, and on-device environments. The platform includes developer SDKs, instant voice cloning, and telephony support.
At a glance
Capability tags are factual labels we assign when a tool is added; they describe what a tool does, not how well it does it.
Checked against the vendors. Written from each vendor's own site and last re-checked there: AssemblyAI on August 31, 2026 · Cartesia (under review since September 3, 2026). Vendors change pricing and features without notice, so confirm anything that decides your purchase on the vendor's page.
Also in audio
A tool we have an affiliate relationship with. It is not part of the comparison above and we are not calling it the better pick.
- Repurposing podcast and video recordings into social posts, newsletters, and blogs
- Content teams and agencies managing multi-brand client media pipelines
- Transcribing and summarizing meetings, webinars, and sales calls
Key features
AssemblyAI
- Pre-recorded and real-time streaming speech-to-text transcription
- Speaker diarization to segment utterances by speaker
- LLM-powered Speech Understanding and LLM Gateway
- Custom keyterms prompting and Medical Mode for specialized terminology
Cartesia
- Sonic-3.6 text-to-speech model
- Ink-2 streaming speech-to-text transcription
- Managed Agents for building and shipping voice agents
- Cloud, on-premise, and on-device deployment options
- Instant and professional voice cloning
What each one does well
AssemblyAI
- ✓ Building real-time voice agents
- ✓ Transcribing pre-recorded audio files with high accuracy
- ✓ Performing call analytics and medical transcription
Cartesia
- ✓ Building real-time conversational voice agents
- ✓ Low-latency streaming speech transcription and generation
- ✓ Deploying voice AI models on-premise or on-device
People also ask
Which is cheaper, AssemblyAI or Cartesia?
AssemblyAI starts at $0.02 usage-based and Cartesia starts at $5/mo. The two are billed over different periods, so we do not rank them on price.
Does AssemblyAI or Cartesia have a free plan?
Both. AssemblyAI and Cartesia each publish a free plan.
What is the difference between AssemblyAI and Cartesia?
Both are tracked for speech-to-text, transcription. Of the capabilities they do not share, only AssemblyAI is tracked for speaker-identification, developer-api, and only Cartesia is tracked for text-to-speech, voice-cloning, voice-generation, ai-agents.
How much do AssemblyAI and Cartesia cost?
AssemblyAI: free plan, then $0.02 usage-based. Cartesia: free plan, then $5/mo.
Answers are generated from the tracked plans and capability tags shown above, so they move when the vendors' pages do.
Full fact sheets, FAQs, and discussion links: AssemblyAI · Cartesia · all audio tools