Prompt API
#26 in LLM APIs & Gatewaysgoogle · since Chrome 138 · 2× · last seen Jun 30, 2026
12
Momentum
The Prompt API is an interface that enables web pages to directly prompt a browser-provided language model. It was introduced in Chrome 138.
Momentum trend
04.04.03.07.
Features
| Throughput Routing (Intelligence) | No routing between models; the API always forwards to the locally installed Gemini Nano. Inference happens fully on-device, with no network round-trip for generation. |
| Price Tier/Cost Model | Free / no API key, no network round-trip, no token billing. Usage is approved for commercial purposes ("Yes" to the question "Is it free for commercial use?"). |
| Supported LLM Providers | Exclusively Gemini Nano (Google) – local in the browser, 2–4B parameters, quantized. No external cloud provider; the model runs fully on-device. |