Cartesia Line vs OpenAI Realtime API (gpt-realtime)

Cartesia Line and OpenAI Realtime API (gpt-realtime) are both Realtime Voice Agent APIs, compared here on pricing, compliance, capabilities, and developer experience from structured, cited data - not reviews or paid placement. OpenAI Realtime API (gpt-realtime) starts lower at $0.02 per minute vs $0.06 for Cartesia Line. Cartesia Line offers a free tier while OpenAI Realtime API (gpt-realtime) does not, so Cartesia Line is easier to trial before committing. For coding-agent use, Cartesia Line scores higher on agent-friendliness (55 vs 50).

Comparedby a transparent data-readiness score computed from each API's published, sourced fields. No reviews, no paid placement. How we rank.

Data last verified 2026-06-21, with every field cited on each profile.

Head-to-head, from published, cited fields (auto-generated; no paid placement)
Field	Cartesia Line	OpenAI Realtime API (gpt-realtime)
Starting price	$0.06 minute	$0.02 minute (audio input)
Pricing model	Hybrid	Usage
Free tier	✓	✗
Self-serve signup	✓	✓
SOC 2	Type II	Type II
HIPAA	✓	✓
GDPR	✓	✓
Webhooks	✓	✓
Sandbox	✗	✗
Documented actions	25	17

Full data and citations: Cartesia Line · OpenAI Realtime API (gpt-realtime). See more Realtime Voice Agent APIs.