Cartesia vs OpenAI Realtime API

Pick two tools from the same category to compare side-by-side.

	Cartesia Low-latency voice AI platform built around the Sonic text-to-speech model.	OpenAI Realtime API Speech-to-speech realtime model API for building low-latency voice agents.
Category	voice	voice
Vendor type	commercial	commercial
Pricing	freemium	usage
Strengths	+ Ultra-low latency text-to-speech optimized for realtime interaction + State space model architecture aimed at efficiency at scale + Cloud, on-premise, and on-device deployment options + Voice cloning and conversion capabilities	+ Single model handling speech-to-speech with reasoning and tool calling + Multiple transports including WebRTC, WebSocket, and SIP for telephony + Low-latency persistent sessions for natural turn-taking + Specialized variants for live translation and streaming transcription
Tradeoffs	− Proprietary models limit portability compared with open-weight options − Usage-based agent minutes add cost on top of base credits − Newer ecosystem than longer-established voice vendors	− Locked to OpenAI models with no provider choice − Closed, cloud-only API − Realtime audio pricing can be costly at scale
Used in stacks	0	0