Cartesia Line vs Ultravox

Cartesia Line and Ultravox are both Realtime Voice Agent APIs, compared here on pricing, compliance, capabilities, and developer experience from structured, cited data - not reviews or paid placement. Ultravox starts lower at $0.05 per minute vs $0.06 for Cartesia Line. Cartesia Line offers a free tier while Ultravox does not, so Cartesia Line is easier to trial before committing. On compliance, Cartesia Line additionally documents SOC 2, HIPAA, GDPR. For coding-agent use, Cartesia Line scores higher on agent-friendliness (55 vs 20).

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	Ultravox
Starting price	$0.06 minute	$0.05 minute
Pricing model	Hybrid	Usage
Free tier	✓	✗
Self-serve signup	✓	✓
SOC 2	Type II	·
HIPAA	✓	·
GDPR	✓	·
Webhooks	✓	✓
Sandbox	✗	✗
Documented actions	25	20

Full data and citations: Cartesia Line · Ultravox. See more Realtime Voice Agent APIs.