What is Claude Code?

What Claude Code is

Claude Code is a coding agent from Anthropic that runs in your terminal. It reads the files in a real repository, edits them, runs commands such as npm test or git commit, and reads the output to decide what to do next. You describe a task in plain language and it does the work in your working directory.

A chat window can only hand you text to copy back into your editor. Claude Code holds the file system and the shell, so it changes the code, runs the tests, sees the failure and fixes it without you carrying text between two windows.

Starting a session on macOS, Linux or WSL (Windows Subsystem for Linux) takes three commands:

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

The first run opens your browser to log in. After that, claude --version prints a version number followed by (Claude Code). If your shell answers claude: command not found instead, the launcher was installed to ~/.local/bin, and a shell you opened before the install does not have that directory on its PATH yet. Open a new terminal and run it again. claude doctor prints installation and settings diagnostics without starting a session, which is the fastest way to see what a broken install is missing.

Where does Claude Code run?

The terminal is the main surface. It supports macOS 13.0 and newer, Windows 10 1809 and newer, Ubuntu 20.04 and newer, Debian 10 and newer, and Alpine 3.19 and newer, on x64 or ARM64 hardware with at least 4 GB of RAM. Bash, Zsh, PowerShell and CMD all work.

The same engine drives the other surfaces: extensions for VS Code and JetBrains IDEs, a desktop app, the browser at claude.ai/code, and the Claude mobile app. Your repository's CLAUDE.md file, your settings and your MCP (model context protocol) servers apply on all of them, so moving between surfaces does not mean configuring anything twice.

An internet connection is required, because the model itself runs on Anthropic's servers. Your machine runs only the agent loop: the file reads, the edits and the shell commands. Nothing here works offline.

That split is why a small server makes a good host. A long task holds a terminal open for as long as it runs, so people put the agent on a VPS, start it inside tmux over SSH, and then close the laptop without killing the session. Running Claude Code on a VPS inside tmux walks through that setup. For a machine sitting in front of you instead, Claude on the Linux desktop and the CLI covers the local install.

What does Claude Code cost?

There are two ways to pay for it, and they behave differently.

A Claude subscription includes Claude Code. The Pro, Max, Team and Enterprise plans all carry it, and your usage is bounded by the plan's rolling limits rather than by a bill that keeps growing. When you reach a limit you wait for the window to reset.

An Anthropic Console account bills per token instead. There is no cap and no reset, so a long agent session on a large repository costs real money in real time. That is the honest cost driver here: the agent pays for every token it reads, and an agent exploring a big codebase reads a lot of it. The same task in a small, tidy repository costs less than in a sprawling one.

Plan prices move, so this page quotes none of them. What Claude Code costs per month carries the current numbers and the arithmetic for choosing between a subscription and per-token billing.

Is Claude Code free?

No. As of August 2026, Claude Code requires a Pro, Max, Team, Enterprise or Console account, and the free Claude.ai plan does not include it. Signing in with a free account gives you the chat product without the agent.

There is no free tier of the agent and no offline mode, because every turn is a request to a model running on Anthropic's servers. The cheapest honest way to try it is one month of the entry paid plan. Whether Claude Code is included with Claude Pro goes through what a Pro plan does and does not cover.

What Claude Code is not

It is not a chat window. It edits files and runs commands on your machine, which is why it asks permission before actions that change something, and why many people run it in a container or on a server they can rebuild.

It is not an IDE. There is no editor pane and no file tree. It attaches to the editor you already use, or to no editor at all.

It is not an autocomplete tool. It does not offer the next line while you type. The unit of work is a whole task, such as "find why this test is flaky and fix it".

It is not a local model. The weights are not on your disk, so a machine with no network connection runs nothing.

Readers often ask for a ChatGPT comparison at this point. That is the wrong axis. The chat products answer questions; Claude Code changes a repository. The comparison worth reading is against the other agents that also hold your file system, and Claude Code against Cursor, Codex and Copilot is that comparison.

FAQ

Is Claude Code free to use?

No. As of August 2026 it needs a paid Claude plan (Pro, Max, Team or Enterprise) or an Anthropic Console account billed per token. The free Claude.ai plan gives you the chat product without the agent. There is no trial tier of the agent and no offline mode, since every turn is a request to a model running on Anthropic's servers.

Do I need to know the terminal to use Claude Code?

A little. You need to open a terminal, change directory into your project, and run claude. From there you type in plain language. If the terminal is the blocker, the desktop app and the browser version at claude.ai/code give you the same agent behind a graphical interface, and both need the same paid account.

Does Claude Code send my code to Anthropic?

The parts it reads, yes. The model runs on Anthropic's servers, so any file the agent opens is sent as part of that request. Files it never opens are never sent. If that matters for a repository, start the agent in a directory that holds only what you are willing to send.

Can I leave Claude Code running while my computer is off?

Not on your own machine, because a terminal session dies with the terminal that owns it. Two ways around that. Run it on a VPS inside tmux, where the session survives the SSH disconnect and you reattach later. Or start the task from the browser or the mobile app, where it runs on Anthropic's infrastructure instead of yours.