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Installation, Authentication & First Steps

A Word Before We Begin

Installing Gemini CLI is like meeting a new colleague—someone who's available 24/7 to help with your work, answer questions, and solve problems. In this lesson, you'll install and launch Gemini CLI, which will then automatically guide you through authentication. You'll be up and running in minutes.

Prerequisites: What You Need​

Make sure you have these before starting:

RequirementWhat It IsHow to Check
Node.js 20+Runtime for JavaScript applicationsOpen terminal, type: node --version
npmPackage manager (comes with Node.js)Open terminal, type: npm --version
Internet connectionFor installation and Google authenticationYou have this already ✓
Google accountFor secure authenticationGmail, YouTube, or any Google account

Don't Have Node.js 20+?​

  1. Visit nodejs.org
  2. Download the LTS version (Long Term Support—the stable version)
  3. Follow the installer steps for your operating system
  4. When asked about npm, keep the checkbox checked
  5. Restart your computer

Opening Your Terminal​

Windows: Search "PowerShell" in your Start menu and open it

macOS: Press Cmd+Space, type "Terminal", press Enter

Linux: Press Ctrl+Alt+T (most distributions)

Installation: One Command​

Open your terminal and run this single command:

npm install -g @google/gemini-cli

This command downloads and installs Gemini CLI globally on your computer. You'll see text flowing by—this is normal. Wait for it to complete (usually takes 30-60 seconds).

Verify Installation​

After installation completes, verify it worked:

gemini -v

You should see a version number like 0.4.0 or higher. If you see this, installation is successful! ✓

Authentication & First Launch​

Now comes the magic—Gemini CLI handles authentication automatically. Simply type:

gemini

When you run this command for the first time, Gemini CLI launches and automatically guides you through setup:

Step 1: Choose Your Theme​

Gemini CLI will ask you to select a visual theme for the terminal interface. Choose whichever you prefer—this is just cosmetic. Use arrow keys to select and press Enter.

Step 2: Choose Authentication Method​

You'll see options for authentication:

  • Google login (free tier: 60 requests/min, 1,000 requests/day)
  • Gemini API Key (requires API setup)
  • Vertex AI (requires Google Cloud Project)

Select "Google login" for the free tier. This is the beginner-friendly option.

Step 3: Browser Opens​

Your default web browser will automatically open with Google's login page. Simply:

  1. Enter your Google account email
  2. Enter your password
  3. Click "Allow" when Google asks for permission

Step 4: You're In!​

After you authorize, your terminal displays the Gemini CLI interface, and you're ready to start. You'll see a prompt where you can type your questions and commands.

Understanding the Gemini CLI Interface​

When you're inside Gemini CLI, notice these important elements:

Bottom Status Bar:

  • Left side: Your current working directory (folder)
  • Middle: The model being used (usually gemini-2.5-pro)
  • Right side: Remaining context tokens (how much "memory" is available)

Useful Commands:

  • Type /help to see all available commands
  • Type /tools to see what tools Gemini can use
  • Type /stats to see session statistics (tokens used, duration, etc.)
  • Type /quit or press Ctrl+C twice to exit

Shell Mode:

  • Type ! to switch to shell mode (run terminal commands directly)
  • Press ESC to exit shell mode

Your First Task with Gemini​

Now that you're inside Gemini CLI, you're ready to put your AI collaborator to work. Simply type your question or request and press Enter:

Help me understand what artificial intelligence means

Gemini will respond with an explanation. That's it—you're using Gemini CLI!

Understanding the Gemini CLI Session​

When you run gemini, you're entering an interactive session. Inside this session, you have access to powerful commands and can ask Gemini multiple questions without exiting.

Basic Session Commands​

These slash commands work inside Gemini CLI:

  • /help - See all available commands and shortcuts
  • /tools - View all available tools Gemini can use
  • /stats - See session statistics (tokens used, duration, etc.)
  • /quit - Exit Gemini CLI and return to your terminal

How to Exit Gemini​

To exit Gemini CLI, simply type:

/quit

Or press Ctrl+C twice to force quit.

Shell Mode (Running Terminal Commands)​

You can run terminal commands directly inside Gemini without exiting:

  • Type ! to enter shell mode
  • Run any terminal command
  • Press ESC to exit shell mode and return to Gemini

Real-World Workflow: Inside a Gemini Session​

Here's what a typical session looks like:

Step 1: Launch Gemini

gemini

Step 2: Inside the session, ask your first question

Explain machine learning to me in simple terms with a real example

Step 3: Gemini responds

Machine learning is a method where computers learn from data...
[Gemini's detailed response]

Step 4: Ask a follow-up question

What are some real-world applications of machine learning?

Step 5: Continue the conversation (you can ask as many questions as you want)

How do companies use machine learning to recommend products?

Step 6: When you're done, exit

/quit

Try With AI​

Now that you've installed Gemini CLI, try these prompts to explore what your AI collaborator can do.

Prompt 1: Learn a New Concept​

Explain machine learning to me in simple terms with a real example. Then give me 3 real-world applications of machine learning.

Expected outcome: Clear explanation with concrete examples and practical applications you can understand.

Prompt 2: Write Professional Content​

Write a professional email to my manager about my project status. The project is [describe your situation]. Make it concise and positive.

Expected outcome: Well-structured professional email you can use or adapt.

Prompt 3: Problem Solving​

I'm getting an error when I try to install a package. The error message is: [paste error]. What does it mean and how do I fix it?

Expected outcome: Clear explanation of the error and step-by-step solution.

Prompt 4: Plan and Organize​

I want to learn programming. What programming language should I start with and why? Give me a 4-week learning plan with specific goals for each week.

Expected outcome: Personalized learning recommendation with structured plan you can follow immediately.