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Head to head · Voice agents · October 2026 research run

Gemini Live API vs OpenAI Realtime API

OpenAI Realtime API scores 63.3 (B) on agent readiness against Gemini Live API's 57.1 (C), and leads in 4 of 7 scored categories. Gemini Live API leads on payments & pricing and maintenance & community. Both do voice agents.

Best conversational voice-agent APIs · All 91 voice agents comparisons

Gemini Live APIGoogle · HTTP API C57.1/100#622 of 950 OpenAI Realtime APIOpenAI · HTTP API B63.3/100#400 of 950

Which one, for what

Gemini Live API C

Good for Teams building their own voice or vision assistant on a single speech-to-speech model with function calling and Search grounding, who can run a backend for tokens and audio transport.

Ahead on

  • Payments & pricing, 40 against 20
  • Maintenance & community, 83 against 52

Watch for

The WebSocket guide authenticates with the API key as a key query parameter, and ephemeral tokens as an access_token query parameter.

OpenAI Realtime API B

Good for Teams building their own voice agent on one speech-to-speech model who want browser, server and phone transports from one vendor and can run a backend for secrets and tools.

Ahead on

  • Reliability, 67 against 41
  • Schema & documentation, 84 against 66
  • Agent ergonomics, 76 against 69
  • Security & auth, 61 against 48

Watch for

openai.com answered 403 to our reader, so the service terms, privacy policy, sub-processor list and security pages were not read.

Score by category

CategoryWeight this runGemini Live APIOpenAI Realtime APIEdge
Reliability16%204167OpenAI Realtime API +26
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.26684OpenAI Realtime API +18
Agent ergonomics13%16.26976OpenAI Realtime API +7
Security & auth14%17.54861OpenAI Realtime API +13
Payments & pricing10%12.54020Gemini Live API +20
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.88352Gemini Live API +31
Transparency & trust7%8.87271Gemini Live API +1
Negative events≤1500
Total57.1 · C63.3 · B

Facts side by side

FactGemini Live APIOpenAI Realtime API
KindHTTP APIHTTP API
VendorGoogleOpenAI
Hosted endpointhttps://generativelanguage.googleapis.com/v1betahttps://api.openai.com/v1/realtime
TransportsHTTPHTTP
AuthAPI keyAPI key
PricingFreemiumPay per use
x402nono
LicenceProprietary service under the Gemini API Additional Terms of Service. The Python and JavaScript SDKs are Apache-2.0Proprietary service. The service terms on openai.com were not read. The Agents SDK for TypeScript and the OpenAPI description are MIT
Read-only variant documentednono
llms.txtyesyes
Last release2026-09-152026-07-28
Terms last updated2026-04-28couldn't be read
Privacy policy last updated2026-10-01couldn't be read
Customer content may train modelsyescouldn't be read
Terms restrict automated accessyescouldn't be read
Terms restrict benchmarkingyescouldn't be read
Terms or service can change without noticenot found in the textcouldn't be read
Arbitration or class-action waivernot found in the textcouldn't be read
Popularity29.5M npm/wk, 34.1M PyPI/wknone

Verdicts

Gemini Live API

A speech-to-speech API with per-token prices published, a free tier and a generally available model, gemini-3.8-live, since 15 September 2026. The documented raw WebSocket connection carries the API key in the URL, connections reset about every 10 minutes, and no SLA or readable incident history was found for the Developer API.

OpenAI Realtime API

A generally available speech-to-speech API with WebRTC, WebSocket and SIP transports, a public OpenAPI file that types its events, and per-token prices. Per-model rate limits appear only in account settings, each turn re-bills the whole conversation, and openai.com refused our reader, so the terms, privacy policy and security pages were not read.

Before you call either

Gemini Live API

  1. Enable sessionResumption and keep the newest handle. Connections end after about 10 minutes, and handles stay valid for 2 hours.
  2. Set contextWindowCompression with a sliding window. Without it audio sessions stop at 15 minutes and audio with video at 2 minutes, and every turn re-bills the whole context.
  3. On gemini-3.8-live function calls are non-blocking by default. Set behavior: BLOCKING if the model must wait for the tool response.
  4. Send 16 kHz 16-bit PCM in 20 to 40 ms chunks and discard buffered playback when interrupted is true.
  5. Keep the API key on a server and send it through the SDK. Give browsers an ephemeral token from POST /v1beta/auth_tokens, locked with liveConnectConstraints.

OpenAI Realtime API

  1. Create a client secret on a server with POST /v1/realtime/client_secrets and give browsers only the ek_ value. Never ship the API key.
  2. After a response with MCP calls finishes, send another response.create. The API does not create the follow-up response itself.
  3. Set truncation with a retention_ratio below 1 and token_limits.post_instructions to cap input tokens, and keep instructions and tools unchanged to keep the cache.
  4. On a WebSocket, stop playback on input_audio_buffer.speech_started and send conversation.item.truncate with audio_end_ms. WebRTC and SIP truncate on the server.
  5. Use gpt-realtime-2.1 or gpt-realtime-2.1-mini. gpt-realtime and gpt-realtime-mini shut down on 20 January 2027.

Questions

Which is better for AI agents, Gemini Live API or OpenAI Realtime API?

OpenAI Realtime API scores 63.3 (B) on agent readiness against Gemini Live API's 57.1 (C), and leads in 4 of 7 scored categories. Gemini Live API leads on payments & pricing and maintenance & community.

Do Gemini Live API and OpenAI Realtime API need an API key?

Both need an API key.

Can an agent call Gemini Live API and OpenAI Realtime API without installing anything?

Yes. Gemini Live API has a hosted endpoint at https://generativelanguage.googleapis.com/v1beta and OpenAI Realtime API at https://api.openai.com/v1/realtime.

Other comparisons with Gemini Live API or OpenAI Realtime API

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