Install Claude Code

This is your first hour with the tool, and the lesson is only slow because every surface is unfamiliar; Take it one step at a time: read the step, do the step, look at what happened, and then move on when the screen matches what the lesson described.

The lesson is short on purpose because you have just paid for a course about a tool you have never opened, and right now you are probably looking at a black or white window you have never voluntarily looked at before, wondering if you are about to break something expensive. You are not; the first hour is only for getting the tool on your machine; you do not need to understand the terminal yet, know what a folder is in a technical sense, or know any code; you need to follow the install path for your operating system and then type six words.

The next lesson teaches you the terminal properly; the lesson after that asks you to write down the thing you wish existed in your life; today is not those lessons; today is the install.

A note before you start. Nothing you do in this lesson can damage your computer. The terminal cannot delete a file you did not tell it to delete. If something looks wrong, close the window and start over. There is no penalty for restarting. If you have ever felt the small panic of “I am about to break my computer,” set that down for the next hour. The install command does one thing. It puts a program on your computer that you can later launch by typing a word.

Three students have just opened this lesson at the same time. A marketing manager in Atlanta on a MacBook Air. A contractor in Cleveland on the Windows laptop his daughter helped him pick out last Christmas. A high school teacher in Albuquerque on a Linux desktop he built himself two years ago. All three are going to finish the lesson tonight. The screens they look at will be different. The commands they type will be different. The version number that comes back at the end will be different. The lesson is the same. So is the result.

What you will have at the end

Three things will be true at the end of the hour.

First, Claude Code will be installed on your computer; you will be able to confirm this by typing six characters into a terminal window and getting back a version number.

Second, a terminal window will be open in front of you, and you will know how to open another one when you want to; you will know what the cursor in that window means; you will know which keystrokes start a session and which keystrokes end it.

Third, you will have typed one sentence to Claude Code and watched it answer; the answer is the proof, and that answer is the moment the tool stops being an idea and starts being a thing you can use.

There is no file to save today; no folder to make; no artifact in the formal sense; tomorrow’s lesson is where you start making things; today is the install.

Section 1. What Claude Code actually is

Claude Code is a tool that runs in your terminal; you type a sentence in plain English; Claude reads it, decides what to do, and either answers you or makes a change to a file on your computer; it can write documents, build websites, run small programs, and edit files you point it at; it does all of this through one window.

It is not a chatbot you visit on a website; it is not a desktop app with menus and buttons; it is a command-line tool, and that means you launch it by typing its name into a terminal, and you talk to it by typing sentences into the same window.

Claude Code lives in a terminal because the terminal already has access to your folders, your files, and the small programs your computer uses to run them; Through that access, Claude Code can do work that lands on your machine instead of staying inside a chat window. If you ask it to write a proposal, the proposal becomes a real file in a real folder you can open with Finder or File Explorer; if you ask it to edit that proposal, it edits the file in place; the terminal is the doorway, and Claude Code is the worker who walks through it.

It is also worth saying what Claude Code is not, so you do not arrive at the second lesson with the wrong expectation; Claude Code is not an automatic button that runs in the background, watches your other apps, or starts working before you ask. It does nothing until you type a sentence and press Enter, and when you close the window, it stops; the next time you open a terminal and type claude, you start a new session, so the tool remains patient until you give it work.

You do not need to understand any of this to use it; you only need to know that one command starts it, and one command ends it; Everything in between is English.

Section 2. Open your terminal

A terminal is the window where you type instructions to your computer instead of clicking on icons; it is already on your machine; you do not install it; you open it.

Below are three paths; pick the one for your operating system; Do that one; skip the other two; the lesson will remember your choice when it matters later in this unit, so the next time a step has Mac and Windows and Linux variants, you will only see the one that matches the choice you make right now.

You cannot break anything by opening a terminal because opening it is exactly as safe as opening any other app on your computer; the terminal is a window, and nothing happens until you type a command and press Enter. Look at the window without typing yet; some students have to read that line twice, which is fine, because the instinct that a terminal is dangerous to look at is real and you are not the only one who has it.

Mac path

Press Cmd+Space; a small search bar opens in the middle of the screen.
Type terminal; the Terminal app appears at the top of the results.
Press Enter; a window opens.

You are now looking at a Terminal window; there is a line of text; it probably ends with % or $; the cursor blinks after that character; that character is called the prompt; the prompt is the terminal’s way of saying it is ready for your next command; Do not type the prompt yourself; it is already there. You type after it.

Windows path

Press the Windows key; the Start menu opens.
Type windows terminal; Windows Terminal appears at the top of the results. If you do not see Windows Terminal, type powershell instead; PowerShell works the same way for this lesson.
Press Enter; a window opens.

You are now looking at a Windows Terminal (or PowerShell) window; there is a line of text; it probably ends with >; the cursor blinks after that character; that character is called the prompt; the prompt is the terminal’s way of saying it is ready for your next command; Do not type the prompt yourself; it is already there. You type after it.

Linux path

Open your application menu; Click Terminal, GNOME Terminal, or Konsole, depending on your distribution.
Or press Ctrl+Alt+T; most distributions open a terminal on that shortcut.
A window opens.

You are now looking at a terminal window; there is a line of text; it probably ends with $; the cursor blinks after that character; that character is called the prompt; the prompt is the terminal’s way of saying it is ready for your next command; Do not type the prompt yourself; it is already there. You type after it.

Section 3. Install Claude Code

You are going to paste one command into your terminal, press Enter, and wait; the install takes between two and five minutes; the screen will scroll while it works; Scrolling is normal; it is showing you what it is doing.

Pick the install path for the operating system you chose above; the other paths still do not apply to you.

Mac path

You picked Mac in Section 2. This is your install path. The contractor in Cleveland and the teacher in Albuquerque are looking at different sections right now.

Make sure your terminal window is open and you can see the prompt; the prompt is the line ending in % or $.
Copy the command below; if you are reading this on the course site, there is a copy button on the right side of the code block. Use it; Two-fingered typing of a command this long is the most common way the install fails before it has even started.
```
curl -fsSL https://claude.ai/install.sh | bash
```
Click once inside the terminal window; the cursor focuses there. Paste the command; On Mac, paste is Cmd+V. You will see the command appear next to the prompt; Read it. Make sure it looks exactly like the command above; if anything is missing or duplicated, press the Delete key until the line is empty and paste again.
Press Enter.

The install runs, and while it works you will see lines of text scrolling; some lines may pause for a few seconds before the next batch appears because the installer is downloading pieces of the tool from the internet. It is not stuck; if your screen sits still for thirty seconds and the prompt has not come back, the install is still working, since internet speeds vary more than a clean walkthrough can show; Wait.

When the install finishes, the scrolling stops and the prompt comes back; you will see a final line that says the install is complete, followed by the same % or $ you saw when you opened the terminal; that returned prompt is the signal that the command finished.

Windows path

You picked Windows in Section 2; this is your install path.

Make sure your Windows Terminal or PowerShell window is open and you can see the prompt; the prompt is the line ending in >.
Copy the command below; Use the copy button on the right side of the code block if you are reading this on the course site. Hand-typing this line is the most common way the install fails before it has even started.
```
irm https://claude.ai/install.ps1 | iex
```
Click once inside the terminal window; Paste the command. On Windows, paste is Ctrl+V, or you can right-click and choose Paste; you will see the command appear next to the prompt. Read it; Make sure it looks exactly like the command above. If anything is missing or duplicated, press the Backspace key until the line is empty and paste again.
Press Enter.

The install runs; you will see lines of text scrolling; some lines may pause for a few seconds; that is the install downloading pieces of the tool; it is not stuck; it is working; if your screen sits still for thirty seconds and the prompt has not come back, it is still working. Wait.

When the install finishes, the scrolling stops and the prompt comes back; you will see a final line saying the install is complete, followed by the same > you saw when you opened the terminal.

Linux path

You picked Linux in Section 2; this is your install path; the install command below works on Ubuntu, Debian, Fedora, Arch, and most distributions in their lineage; if you are on something unusual, the command may need a small adjustment; Run it as written first; if it fails, the troubleshooting section names the most common cause.

Make sure your terminal window is open and you can see the prompt; the prompt is the line ending in $.

Copy the command below.

curl -fsSL https://claude.ai/install.sh | bash

Click once inside the terminal window; Paste the command. On most Linux desktops, paste is Ctrl+Shift+V; you will see the command appear next to the prompt. Read it; Make sure it looks exactly like the command above.
Press Enter.

The install runs; you will see lines of text scrolling; some lines may pause; that is the install downloading pieces of the tool; it is not stuck; it is working; if your screen sits still for thirty seconds and the prompt has not come back, it is still working. Wait.

When the install finishes, the scrolling stops and the prompt comes back.

Shared: close the terminal and open a new one

This step looks small; it is not; Run it on every operating system.

Close the terminal window you used for the install; On Mac, Cmd+Q. On Windows, click the X; On Linux, click the X or press Ctrl+Shift+W.
Open a new terminal window the same way you opened the first one in Section 2.

The reason for this step is plain; the install added Claude Code to the list of programs your terminal knows about; the terminal reads that list when it opens; a terminal window that was already open during the install does not know the list changed; a fresh window does; closing and reopening is how you tell the terminal to refresh.

Section 4. Verify the install worked

You are going to type one short command; it asks Claude Code to say what version of itself is installed; if a version number comes back, the install worked.

The reason to run this small command before doing anything else is honest: install scripts can finish with a confident-looking message and still have failed in a quiet way that only shows up the first time you try to use the tool. The version check is the cheapest possible test; if it passes, the rest of the lesson is straightforward; if it fails, you find out now, with no work invested, instead of finding out two sections later when you are trying to log in.

In the new terminal window, type the command below; you can also copy and paste it.
```
claude --version
```
Press Enter.
Look at the response; you should see one short line with a version number, something like 2.1.139 (Claude Code) or similar. The exact number does not matter for this lesson; what matters is that a number came back.

If nothing happens for two or three seconds, that is normal; the first time you run anything new on a computer, it is the slowest; Wait; the number will come.

If you see a version number, the install is done; the tool is on your machine; the hardest part of the lesson is now behind you; move on to Section 5.

If you see an error like command not found: claude, the install did not finish landing in your computer’s command list; Skip to Section 7; there is a fix for it, and it is the most common fix on the page.

Section 5. Send your first prompt

This is the smallest moment in the course and one of the most useful; you are going to start a session with Claude Code and type one sentence; Claude will answer; that answer is the proof the tool is alive on your machine.

In the same terminal window, type the word below.
```
claude
```
Press Enter.
The first time you run claude, it asks you to log in; your default browser opens a page on claude.ai. Sign in with the same account you used to buy the course; once you are logged in, the page tells you to close it and return to the terminal.

If the browser does not open on its own, the terminal will print a long web address; Copy that address and paste it into a browser yourself; sign in; Return to the terminal.

Back in the terminal, the Claude Code welcome screen now appears; you see the cursor blinking inside a small input box at the bottom of the window. The terminal’s regular prompt is gone for now; you are inside a session.

Type the sentence below, exactly as written.

Say hello and tell me one fact about the number 42.

Press Enter.
Wait; Claude thinks for a few seconds and then prints an answer. The answer will be a short greeting and one fact about the number 42; the exact fact does not matter. What matters is the answer.

That answer is proof that the tool is installed, that your sentence reached it, and that Claude Code can read a plain English request and reply from inside the terminal.

Read what came back and sit with it for a moment, because this is the smallest possible version of every later lesson in the course; you will type a sentence, Claude will do a thing, and the result will appear on your machine; today the thing is one short reply; in Unit 3, the thing will be a proposal you can send to a real client; Same shape, bigger result.

There is one more small thing worth noticing before you exit; the cursor is back; the input box is empty and waiting; you could type another sentence; you could ask Claude what it is good at; you could ask it to count to ten; Anything you type will get an answer; the session keeps running until you end it. Resist the urge to keep going for now; the point of this lesson is the install, not the conversation; the conversation is what the next twenty-six lessons are about.

Section 6. Exit cleanly

You opened a session by typing claude; you close it by typing one command; Closing it cleanly is a habit worth building now, because every later lesson in the course ends with the same two characters.

In the Claude Code session, type the command below.
```
/exit
```
Press Enter.
The session ends; the Claude Code welcome screen disappears. Your terminal’s regular prompt comes back; you are out of the session and back in plain terminal.

If you ever want to come back, type claude again from any terminal window; a new session starts; Claude does not remember the last one; each session is its own conversation; that is by design. In Unit 2 you will learn how to give Claude a small memory file it reads at the start of every session, so it can remember what your project is and who you are even though it does not remember the last conversation; For now, the cleanest mental model is the one in front of you: each session is a fresh start, opened by one word and closed by another.

There is one more way to exit, and you should know it exists even though you will not use it today; if a session ever gets stuck, you can press Ctrl+C two times in a row to force-quit it; that is the emergency stop; Use /exit by default. Save Ctrl+C for when Claude is not responding.

Section 7. Common pitfalls

The install path is well-trodden, but a handful of things still go wrong on a clean machine; each one below has a name, a cause, and a fix; read the symptom column first; if it matches what you are seeing, follow the fix.

command not found: claude after install. What it looks like: you ran claude --version and got back a line that says command not found or claude: not found or something similar. Why it happens: the install added Claude Code to your computer’s list of commands, but your current terminal window was open before that addition; the current window does not know the list changed. How to recover: close every terminal window; Open a fresh one; Run claude --version again; the fresh window reads the updated list. If the error still shows, see the next pitfall.

The install command printed errors and quit. What it looks like: the install ran for a few seconds, printed red or yellow text, and stopped before finishing; the prompt came back but no install completion message appeared. Why it happens: usually a permissions issue, a network hiccup, or a missing tool the installer expected to find (most often curl on a fresh Linux machine). How to recover: run the install command again; Sometimes a second run clears it; if the same error appears, copy the last several lines of the error and search for them; if you are on Linux and the error mentions curl, install curl first with sudo apt install curl on Ubuntu or sudo dnf install curl on Fedora. Then run the install command again.

**The browser did not open during login, and ** What it looks like: you typed claude, pressed Enter, and saw the welcome screen ask you to log in, but no browser tab opened; the terminal printed a long web address; why it happens: some terminal configurations do not automatically open browsers; On Linux servers without a desktop, the terminal has no browser to open. How to recover: select the long web address the terminal printed, copy it, and paste it into any browser; Sign in; close the browser tab; Return to the terminal; the session continues from where it paused.

The version number came back, but claude will not start a session. What it looks like: claude --version works and returns a number, but typing claude by itself prints an error or hangs. Why it happens: rare, and usually a half-finished login; the version command does not need a login; Starting a session does. How to recover: run claude --version once to confirm the install is still good; Then run claude again; if it asks you to log in, you are fine; Sign in through the browser as in Section 5. If it does not ask you to log in and still hangs, close the terminal, open a fresh one, and try again.

The paste did not look right. What it looks like: you pasted the install command, but the line on your screen has extra characters, missing characters, or a strange dash that does not match the dashes in the lesson; Pressing Enter prints an error like command not found or bad substitution. Why it happens: voice-input tools and some keyboard layouts replace the two regular dashes in -- with a single long dash; some terminal emulators on older Windows or Linux setups paste with stray quotes or extra spaces; the command runs on what you actually typed, not what you meant. How to recover: press the Up arrow key in the terminal; the line you just tried to run reappears; Look at it carefully and compare it to the command in the lesson; if the dashes are wrong, the only fix is to copy the command again from the lesson using the copy button and paste it fresh. Do not retype the dashes by hand.

You are on a work computer and the install will not run. What it looks like: the install command starts, prints an error about permissions or a blocked download, and quits; you may see words like access denied, policy, or not permitted. Why it happens: some employers lock down the ability to install new software on company-owned laptops; the lockdown is not personal; it is a setting on the machine. How to recover: if this is a personal laptop with strange permissions, the previous pitfall about the install printing errors is the one to read; if this is genuinely a work-locked machine, the course is not the right place to fight that fight; Run the course on a personal computer at home, or ask your IT department whether they can grant an exception for educational software. Do not run the install command with elevated privileges (sudo on Mac or Linux, or “Run as Administrator” on Windows) to force it past a policy you were not meant to get past; that is the one move on this list that can actually cause problems.

If none of these match what you are seeing, you have hit something the course did not anticipate; that is allowed; go to the course support channel and post the exact error; Include your operating system and the command that produced it; someone will answer.

Section 8. What you walk away with

An hour ago you had a computer with no Claude Code on it; Right now you have a computer with Claude Code installed, a terminal you have opened and closed twice, and a short reply from Claude printed on your screen; you have proof, on your own machine, that the tool is real.

The marketing manager in Atlanta, the contractor in Cleveland, and the teacher in Albuquerque all walked through the same lesson tonight on three different machines. Different keystrokes. Different paste shortcuts. Different scrolling speeds during the install. Same outcome. All three closed their first session with /exit and watched the regular terminal prompt come back. So did you.

Tomorrow’s lesson teaches you what a terminal is; you will learn three commands and the small mental model that holds them together; After that lesson, the terminal stops being a window full of unfamiliar text and starts being a place you know how to move around in. The version check you ran tonight will look small in retrospect; it is the floor the rest of the course stands on.

The lesson after that asks you to write down the thing you already wish existed in your life; Not a business plan; not a pitch; a description of something you have been quietly thinking about; that description becomes the project you build for the rest of the course.

For now, none of that matters; you opened a terminal; you ran one install command; you typed a sentence; the tool answered; that is the entire lesson; Close the laptop or move to the next one when you are ready. The install does not go away.

Auto-grader rubric

Three static checks; all three must pass before you move to Lesson 0.2, and these are the lowest possible bar for “the install worked,” and that is the right bar for a foundational lesson; Mastery on the small things is what makes the larger things possible.

Check 1. claude --version returns a version string on your machine. Run it once. A number comes back. The number itself does not matter. The fact that any number comes back is the signal.
Check 2. A login token exists in ~/.claude/ on your computer. This is created automatically the first time you sign in through the browser in Section 5. You do not need to look at the token. You do not need to know where it lives in detail. It exists or it does not. If claude started a session and let you type a prompt, the token exists.
Check 3. A clean claude and /exit cycle runs without errors. Start a session, watch the welcome screen appear, type /exit, and watch the regular terminal prompt come back. If you completed Section 5 and Section 6, you have already done this once.

If all three pass, you are done; close the terminal; the next lesson opens with the same window you just closed, and the same prompt waiting for you.