What is Claude Code?

Claude Code is Anthropic's AI coding agent. It is not a chat interface with a code block. It is an agent that runs inside your terminal, reads your actual codebase, makes changes to files, runs commands, and iterates on your work. It can go from a natural language instruction to a working feature without you touching a file.

Built on Claude Sonnet 4.6, it is one of the most capable coding tools available right now. If you are a developer who has not tried it yet, it is worth your time.

What it's actually good for

Building features from scratch. You describe what you want in plain English and Claude Code reads your existing code, understands the context, and implements the feature. It follows your naming conventions, imports from the right places, and writes code that fits the project rather than generic boilerplate.

Debugging. Give it an error message, point it at the relevant file, and it will trace the problem. It can run your test suite, look at the output, and iterate until the tests pass. This is where agentic AI earns its place. It does not just guess. It checks its work.

Code review. Paste in a pull request or point it at a file and ask for a review. Claude Code will identify potential issues, suggest improvements, and explain its reasoning. Useful whether you are a solo developer or working in a team.

Refactoring. Ask it to clean up a messy function, improve readability, add error handling, or convert a file to TypeScript. It reads the surrounding context before making changes, so the refactor tends to make sense in the wider project.

Documentation. Getting documentation written is something most developers put off. Claude Code will read your functions and write clear, accurate docstrings and README sections in a fraction of the time.

The 1 million token context window

Claude Code benefits from Claude's 1 million token context window. That is roughly 750,000 words, or the equivalent of an entire book. In practice, it means Claude Code can read a large, complex codebase in a single pass, understand the relationships between files, and make changes that are coherent across the whole project rather than just the file in front of it.

For smaller projects this is not noticeable. For larger ones, it is a significant advantage over tools that lose track of earlier context mid-session.

How it compares

Claude Code sits alongside GitHub Copilot, Cursor, and OpenAI's Codex in the agentic coding space. Where Copilot works mainly as an IDE autocomplete, Claude Code operates at a higher level of abstraction. You work with it in your terminal and give it goals, not just suggestions to accept or reject.

It is well suited to developers who want to stay in their existing editor setup and do not want to switch to a purpose-built AI IDE.

Who should use it

Claude Code is for developers. It requires comfort with the terminal and assumes you know enough to review what it produces. It is not a no-code tool. That said, it is genuinely useful across a wide range of experience levels, from junior developers learning a new codebase to senior engineers accelerating complex work.

How to get set up

Subscribe to Claude Pro at claude.ai (£18/month)
Open your terminal
Run npm install -g @anthropic-ai/claude-code
Run claude in the root of your project
Follow the authentication prompts to connect your Claude account
Type your first instruction: for example, "read this codebase and explain the structure"

Time to get started: Under 10 minutes Do you need a credit card? Yes, Claude Pro is required at £18/month

Claude Code