Claude is Anthropic's AI assistant — and the one most developers, writers, and analysts reach for when accuracy and reasoning quality actually matter. This guide covers everything from setup to advanced features that separate power users from casual ones.
What Makes Claude Different
Claude is built by Anthropic with a focus on safety and helpfulness. The key advantages in practice:
- 200K token context window — paste entire codebases, long documents, full transcripts
- Artifacts — Claude creates standalone files (code, documents, diagrams) you can edit and export
- Projects — persistent memory across conversations, per-project
- Exceptional instruction-following — Claude stays on task better than most models
Getting Started
- Go to claude.ai — free plan includes Claude Sonnet
- Claude Pro ($20/month) gives access to Claude Opus (the most capable model) with 5x more usage
- API access at console.anthropic.com for developers
No complex setup. Start chatting immediately.
The 4 Features That Matter Most
1. Projects (Persistent Context)
Projects let Claude remember your preferences, codebase, or documents across sessions. Create one for each client, product, or topic.
How to use it:
- Click New Project in the sidebar
- Upload files or paste content into the project knowledge base
- Add instructions: "Always respond in formal English. This is a SaaS B2B product."
- Every new conversation in this project inherits that context
Real use: drop your entire codebase into a project. Ask Claude to explain any function, find bugs, or suggest refactors — it has the full picture.
2. The 200K Context Window
Claude can process ~150,000 words in a single conversation. What this unlocks:
- Paste a full legal contract: "Summarize the key obligations and flag anything unusual"
- Drop an entire codebase: "What's the overall architecture? Where would I add authentication?"
- Upload a 200-page PDF: "Create a table of contents and a 3-paragraph summary"
Practical tip: when pasting large documents, tell Claude what to focus on. Don't just dump text — give it a question.
3. Artifacts
When Claude creates a document, code file, or structured output, it opens in a separate panel as an Artifact — a live, editable file.
Artifacts work for:
- Code: runs in a preview panel (HTML/CSS/JS), can be downloaded
- Documents: formatted Markdown, exportable
- SVG/Diagrams: renders visually
- React components: live preview
To trigger: just ask for something that has a natural file form. "Create a landing page in HTML" → Artifact. "Write a project proposal" → Artifact.
4. Extended Thinking (Claude Opus)
With Claude Opus and Extended Thinking enabled, Claude shows its reasoning chain before answering. Use this for:
- Complex multi-step problems
- Math or logic questions where the answer matters
- Strategic decisions where you want to see the tradeoffs
Enable it: New conversation → Extended thinking toggle (Pro plan required).
Prompting Claude Effectively
Claude is trained to follow detailed instructions, so specificity pays off.
Weak: "Write a blog post about AI"
Strong: "Write a 700-word blog post for a non-technical audience about how AI image generators work. Use a friendly, conversational tone. Structure: intro hook, how-it-works explanation with an analogy, 3 practical use cases, brief conclusion with a call to action."
System Prompt Equivalent
At the start of a conversation, set the context:
You are an expert tax accountant specializing in US freelance/contractor taxation.
The user is a software developer earning $180K/year as a W-2 employee plus $40K from freelance work.
Always cite IRS publications when giving specific advice.
Respond in plain language, avoid jargon.
This "primes" Claude and improves every subsequent answer in that conversation.
The Best Use Cases for Claude
| Use case | Why Claude |
|---|---|
| Long document analysis | 200K context, accurate extraction |
| Code review and debugging | Strong reasoning, catches subtle bugs |
| Technical writing | Precise, follows complex style guides |
| Legal/contract review | Careful, flags edge cases |
| Research summarization | Synthesizes well, cites reasoning |
| Data analysis (with CSV) | Can analyze tables and find patterns |
Claude vs ChatGPT: When to Use Which
Claude is generally better for tasks requiring careful reasoning, long context, and precise instruction-following. ChatGPT (with plugins/browsing) is better when you need real-time web access or integrations.
For detailed benchmarks and use cases, see the Claude vs ChatGPT comparison.
Read the full Claude review for model-by-model breakdowns (Haiku, Sonnet, Opus).