Gemini API Cheatsheet 2026 — Free Tier Limits, Models, and Endpoints in One Place

Source: Dev.to

Model Overview

Recommended Model

For most use cases: gemini-2.5-flash-preview

Rate Limits

RPM = requests per minute, TPM = tokens per minute, RPD = requests per day.

API Examples

Generate Content (cURL)

curl https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash-preview:generateContent \
  -H "Content-Type: application/json" \
  -H "x-goog-api-key: YOUR_API_KEY" \
  -d '{
    "contents": [{"parts": [{"text": "Your prompt here"}]}]
  }'

Stream Generate Content (cURL)

curl https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash-preview:streamGenerateContent \
  -H "Content-Type: application/json" \
  -H "x-goog-api-key: YOUR_API_KEY" \
  -d '{"contents": [{"parts": [{"text": "Tell me a story"}]}]}'

Rust Example (reqwest)

use reqwest::Client;
use serde_json::json;

pub async fn call_gemini(prompt: &str, api_key: &str) -> Result {
    let client = Client::new();
    let url = format!(
        "https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash-preview:generateContent?key={}",
        api_key
    );

    let body = json!({
        "contents": [{ "parts": [{ "text": prompt }] }]
    });

    let res = client.post(&url).json(&body).send().await?;
    let data: serde_json::Value = res.json().await?;

    let text = data["candidates"][0]["content"]["parts"][0]["text"]
        .as_str()
        .unwrap_or("")
        .to_string();

    Ok(text)
}

Error Codes

Token Estimates

• 1 token ≈ 4 characters in English
• 1 token ≈ 2–3 characters in Japanese
• 100 lines of Logcat ≈ 3 000–5 000 tokens
• 1 page of PDF text ≈ 500–800 tokens

Getting an API Key

1. Go to aistudio.google.com.
2. Sign in with Google.
3. Click “Get API Key.”
4. No credit card is required.

Related Links

• Hiyoko PDF Vault → (by @hiyoyok)