Compare realtime APIs
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| Telnyx Voice AI (AI Assistants) Telnyx | Millis AI Millis AI | Twilio ConversationRelay Twilio | |
|---|---|---|---|
| Category | Platforms | Platforms | Platforms |
| Status | GA | GA | GA |
| Est. per minute | $0.06 - 0.09 | $0.04 - 0.09 | $0.08 - 0.12 |
| How that was worked out | Telnyx's own 'realistic all-in' is about $0.06/min (example: ~$13,700/month at 230,000 minutes) with an open model on Telnyx GPUs. High end assumes a frontier OpenAI/Anthropic model and outbound calls. Excludes 60-second per-call rounding. | $0.02 + $0.0043 STT + ~$0.004 LLM + $0.0075-$0.05 TTS + your carrier minutes (~$0.005-$0.014). Third-party worked example: ~$0.066/min with GPT-4o + ElevenLabs. | $0.07 ConversationRelay + $0.0085 inbound or $0.014 outbound + your own LLM (roughly $0.002-0.03/min depending on model). Assumes STT/TTS are included in the $0.07 as third parties report. |
| Pricing model | per-minute | per-minute | per-minute |
| Free tier | No free usage credits listed; $0 monthly fee on pay as you go. | Not published. | Twilio trial credit only. |
| Connects by | PSTN, SIP, WebSocket, WebRTC | WebRTC, WebSocket, PSTN, SIP | PSTN, SIP, WebSocket |
| Audio in | Phone/SIP; WebSocket to assistant | Web SDK and phone (via your Twilio/Plivo etc.) | Phone call; Twilio does STT and sends text to you |
| Audio out | Same | Same | You send text tokens; Twilio does TTS |
| Languages | Not verified per voice; depends on STT/TTS chosen. | Not verified. | Many via Google/Deepgram STT and ElevenLabs/Google/Amazon voices; 'multi' auto-detect requires Deepgram + ElevenLabs. |
| Latency (vendor claim) | Vendor claims sub-500 ms end-to-end on marketing pages (vendor claim, not verified). | Vendor markets very low latency; no verified number. | No verified number. |
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| Compliance | Site footer lists ISO, PCI, HIPAA, GDPR, SOC 2 Type II; Voice AI BAA scope not verified. | Not verified. | HIPAA eligible with a signed BAA (per TwiML docs); Twilio-wide SOC 2/GDPR programs not re-verified here. |
| Self-hostable | No | No | No |
| Last checked | 2026-10-10 | 2026-10-10 | 2026-10-10 |
| Key numbers and features | |||
| Platform $/min | $0.05 | $0.02 | $0.07 |
| All-in price | No | No | No |
| Entry plan $/mo | $0 | $0 | $0 |
| Free tier | No | - | Yes |
| Free credit $ | - | - | - |
| Phone numbers | Yes | Yes | Yes |
| Own LLM | - | Yes | Yes |
| Own keys | - | - | - |
| No-code | Yes | - | - |
| Recording | - | - | Yes |
| Noise cancel | - | - | - |
| Smart turns | - | - | Yes |
| Latency ms | 500 | - | - |
| Languages | - | - | - |
| Max session min | - | - | - |
| Concurrency | 500 | - | - |
| WebRTC | Yes | Yes | - |
| WebSocket | Yes | Yes | Yes |
| Phone / SIP | Yes | Yes | Yes |
| HIPAA | - | - | Yes |
| SOC 2 | Yes | - | - |
| EU data | Yes | - | - |
| Self-host | No | No | No |
| Open weights | No | No | No |
| High warnings | 0 | 0 | 0 |