What is Claude Code and how is it different from using Claude in the browser?

Claude Code is a command-line tool made by Anthropic that runs Claude as an autonomous coding agent directly in your terminal. Unlike the browser chat where you copy-paste code back and forth, Claude Code can read your actual project files, write and edit code, run terminal commands, execute tests, and fix errors — all without you doing it manually.

To install Claude Code, you need Node.js installed, then run npm install -g @anthropic-ai/claude-code in your terminal. Navigate to your project folder and run claude to start a session. You can then give it high-level instructions like add input validation to all form fields and it will go through your codebase and make the changes.

The key difference from browser chat is autonomy. In the browser you are the one applying the suggestions. With Claude Code, it takes actions itself — reading files, editing them, running your test suite, and iterating until the tests pass. It is far more efficient for real development work on an actual codebase.

Claude Code is best for tasks like refactoring existing code, adding features to a project, fixing bugs across multiple files, writing unit tests, or understanding a large unfamiliar codebase. For quick one-off questions or when you just need a snippet explained, the browser chat is still perfectly fine.

Claude Code uses the same underlying Claude models but with additional tools that let it interact with your filesystem and shell. It keeps a context of everything it has read and done in the session, so it can make coherent multi-step changes across an entire project rather than just responding to one message at a time.