# Gemini Live API vs OpenAI Realtime API

> OpenAI Realtime scores 63.3 (B) to Gemini Live's 57.1 (C) for voice agents. Prices, MCP, x402, uptime and agent notes side by side.

- Canonical: https://www.anchorterminal.com/compare/gemini-live-vs-openai-realtime
- Markdown: https://www.anchorterminal.com/compare/gemini-live-vs-openai-realtime.md (~2,750 tokens)
- Slim: https://www.anchorterminal.com/compare/gemini-live-vs-openai-realtime.min.md (~780 tokens, same facts, less prose, for token-sensitive contexts)
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- Site index for agents: https://www.anchorterminal.com/llms.txt (full text: https://www.anchorterminal.com/llms-full.txt)
- API: https://www.anchorterminal.com/api/v1/index.json
- Updated: 2026-10-09

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.

- Gemini Live API: grade C, 57.1/100, rank #622 of 950. Markdown https://www.anchorterminal.com/tools/gemini-live.md · JSON https://www.anchorterminal.com/api/v1/tools/gemini-live.json
- OpenAI Realtime API: grade B, 63.3/100, rank #400 of 950. Markdown https://www.anchorterminal.com/tools/openai-realtime.md · JSON https://www.anchorterminal.com/api/v1/tools/openai-realtime.json
- Best conversational voice-agent APIs: https://www.anchorterminal.com/best/voice-agents/index.md
- All 91 voice agents comparisons: https://www.anchorterminal.com/compare/voice-agents/index.md

## 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

| Category | Weight | Gemini Live API | OpenAI Realtime API | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 41 | 67 | OpenAI Realtime API +26 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 66 | 84 | OpenAI Realtime API +18 |
| Agent ergonomics | 13% (16.2 this run) | 69 | 76 | OpenAI Realtime API +7 |
| Security & auth | 14% (17.5 this run) | 48 | 61 | OpenAI Realtime API +13 |
| Payments & pricing | 10% (12.5 this run) | 40 | 20 | Gemini Live API +20 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 83 | 52 | Gemini Live API +31 |
| Transparency & trust | 7% (8.8 this run) | 72 | 71 | Gemini Live API +1 |
| Negative events | ≤15 | 0 | 0 | |
| **Total** | | **57.1 · C** | **63.3 · B** | |

## Facts side by side

| Fact | Gemini Live API | OpenAI Realtime API |
| --- | --- | --- |
| Kind | HTTP API | HTTP API |
| Vendor | Google | OpenAI |
| Hosted endpoint | `https://generativelanguage.googleapis.com/v1beta` | `https://api.openai.com/v1/realtime` |
| Transports | HTTP | HTTP |
| Auth | API key | API key |
| Pricing | Freemium | Pay per use |
| x402 | no | no |
| Licence | Proprietary service under the Gemini API Additional Terms of Service. The Python and JavaScript SDKs are Apache-2.0 | Proprietary service. The service terms on openai.com were not read. The Agents SDK for TypeScript and the OpenAPI description are MIT |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| Last release | 2026-09-15 | 2026-07-28 |
| Terms last updated | 2026-04-28 | couldn't be read |
| Privacy policy last updated | 2026-10-01 | couldn't be read |
| Customer content may train models | yes | couldn't be read |
| Terms restrict automated access | yes | couldn't be read |
| Terms restrict benchmarking | yes | couldn't be read |
| Terms or service can change without notice | not found in the text | couldn't be read |
| Arbitration or class-action waiver | not found in the text | couldn't be read |
| Popularity | 29.5M npm/wk, 34.1M PyPI/wk | none |

## 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.


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/gemini-live-vs-openai-realtime.json, and with the fewest tokens: https://www.anchorterminal.com/compare/gemini-live-vs-openai-realtime.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "gemini-live", "b": "openai-realtime"}`. From a terminal: `anchor compare gemini-live openai-realtime`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/gemini-live.json and https://www.anchorterminal.com/api/v1/tools/openai-realtime.json

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