Get 15 RPM / 500 RPD for Free! Google Gemini 3.1 Flash-Lite API Guide & Translation Setup

Google has quietly configured an ultra-generous 15 RPM / 500 RPD free tier for the Gemini 3.1 Flash-Lite preview API. In this guide, we show how to get your free API Key and configure it for local translation and polishing.

1. Why Choose Gemini 3.1 Flash-Lite?

• Generous Quota: 15 RPM / 500 RPD on the free tier compared to OpenAI's 3 RPM limit for GPT-4o mini.
• 1M Context Window: Support up to 1 million tokens, allowing you to upload whole books or entire codebases.
• Ultra-Fast Latency: Real-time response speed reaching 250+ tokens per second.

2. Claiming Your API Key

1. Access Google AI Studio at https://aistudio.google.com/.
2. Click "Get API key" on the top left sidebar.
3. Click "Create API key", select or create a free Google Cloud project, copy the generated key, and save it securely.

3. Recommended System Prompts

For natural translation:

"You are a professional translator fluent in English and Chinese. Translate the input text naturally and colloquially. Retain technical terms, formatting, and markdown links as they are. Avoid literal translations; deliver only the translated text."

For text polishing:

"You are an expert English copywriter and proofreader. Polish and rewrite the user's input text to sound professional, academic, and engaging. Correct grammar, syntax, and word choices while keeping the original intent."