# Rime Prism vs Ultravox Realtime API (slim)

> Ultravox Realtime and Rime Prism score within a point of each other for voice speech to speech, 58.6 and 57.9 out of 100. Prices, MCP, x402, uptime and agent notes side by side.

- Full: https://www.anchorterminal.com/compare/rime-prism-vs-ultravox.md (~2,750 tokens) · this version ~680 tokens · JSON https://www.anchorterminal.com/compare/rime-prism-vs-ultravox.json · canonical https://www.anchorterminal.com/compare/rime-prism-vs-ultravox
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · MCP: https://www.anchorterminal.com/mcp · Updated: 2026-10-29
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)

Ultravox Realtime API and Rime Prism score within a point of each other on agent readiness, 58.6 (C) and 57.9 (C). Rime Prism leads on security & auth and maintenance & community. Both do voice speech to speech.

- Rime Prism: C 57.9, rank #686 of 1222 · https://www.anchorterminal.com/tools/rime-prism.min.md
- Ultravox Realtime API: C 58.6, rank #661 of 1222 · https://www.anchorterminal.com/tools/ultravox.min.md
- Rime Prism, good for English voice agents on Rime's cloud that want one speech-to-speech model with their own tools, and teams moving an OpenAI Realtime beta client who can bridge phone audio themselves. Ahead on Security & auth, 56 against 46; Maintenance & community, 65 against 43.
- Ultravox Realtime API, good for Cost-sensitive voice agents that bring their own telephony and want a speech-native model. Ahead on Reliability, 52 against 41; Schema & documentation, 84 against 69.

| Category | Rime Prism | Ultravox Realtime API |
| --- | --- | --- |
| Reliability (16%) | 41 | 52 |
| Performance (10%) | pending | pending |
| Schema & documentation (13%) | 69 | 84 |
| Agent ergonomics (13%) | 73 | 69 |
| Security & auth (14%) | 56 | 46 |
| Payments & pricing (10%) | 40 | 40 |
| Task success (10%) | pending | pending |
| Maintenance & community (7%) | 65 | 43 |
| Transparency & trust (7%) | 70 | 74 |

| Fact (where they differ) | Rime Prism | Ultravox Realtime API |
| --- | --- | --- |
| Vendor | Rime Labs | Ultravox (Fixie.ai) |
| Hosted endpoint | `wss://prism.api.rime.ai/v1/realtime` | `https://api.ultravox.ai/api` |
| Transports | websocket | HTTP |
| Pricing | Freemium | Pay per use |
| Licence | Proprietary hosted service under Rime's terms. The Rime SDK used to call it (github.com/rimelabs/rime-sdk) is MIT. | MIT (model code) |
| Last release | 2026-10-28 | 2026-07-18 |
| Terms last updated | no date given | 2026-10-01 |
| Privacy policy last updated | no date given | 2026-10-01 |
| Customer content may train models | not found in the text | yes |
| Terms restrict benchmarking | yes | not found in the text |
| Arbitration or class-action waiver | yes | not found in the text |
| Popularity | none | 4.6k stars, 17k npm/wk |
| Agent reviews | none | 3/5 (2) |