What Is Claude AI? Anthropic's AI Assistant Explained

Originally published on CodingCush.

Claude is the AI assistant made by Anthropic, an AI safety company founded in 2021 by former OpenAI researchers. Like other top assistants, Claude answers questions, writes, summarises and codes, but it has built a particular reputation for careful, low-fluff answers, patient work with very long documents, and strong coding help. Anthropic trains Claude with a method called Constitutional AI, where the model is guided by a written set of principles it uses to judge and improve its own answers. If you want the thoughtful colleague rather than the loud one, Claude is usually the name people suggest.

Who Makes Claude?

Anthropic was founded in 2021 by a group of researchers who had previously worked at OpenAI, including siblings Dario and Daniela Amodei. The company focuses on AI safety research, and Claude is its main product. The Constitutional AI approach works like this: instead of only training the model on human ratings, Anthropic gives it a constitution, a list of principles about being helpful, honest and harmless, and trains the model to critique and revise its own responses against those principles. You can explore the current models on the official Claude page at Anthropic.

Whether or not you care about the philosophy, the practical effect is easy to notice. Claude tends to admit uncertainty, avoids over-promising, and writes in a calm tone that suits professional work. It is the assistant many writers, researchers and developers open when the task is long and the details matter.

The official Claude pricing page on claude.com: Free, Pro, Max and Ultra, with Claude Code included on the paid plans.

The Current Claude Models (November 2026)

Anthropic's line-up has four tiers, and the whole family shares a very large 1 million token context window, which means Claude can hold entire codebases or book-length documents in mind during one conversation:

• Fable 5.2, released on 9 November 2026, is the top tier, built for the hardest technical work where you want maximum reasoning power.
• Opus 5.5 is the recommended everyday default for most subscribers: very capable, and sensible for daily professional work.
• Sonnet 5.5 is the balanced option, quick and smart in equal measure.
• Haiku 5.5 is the fastest and cheapest tier, ideal for high-volume simple tasks.

A 1 million token window sounds like a spec-sheet number until you paste a 400-page PDF or a full project folder into the chat and Claude simply gets on with it. For document-heavy work, that is the feature people end up caring about most.

What Can You Do with Claude?

Beyond plain chat, Claude's feature list has grown into a small toolbox:

• Artifacts turn answers into living documents, code, charts and mini-apps in a side panel that you can edit and reuse.
• Projects give you workspaces with their own files and instructions, so ongoing work keeps its context.
• Research mode sends Claude off to search and read multiple sources, then returns a report with citations.
• Claude Code is Anthropic's terminal-based coding agent, which can work through real programming tasks in your project folder.
• Cowork and Claude in Chrome extend Claude into collaborative work and your browser.
• File analysis and vision let you upload spreadsheets, documents and images and ask questions about them.

Developers often meet Claude first through coding. If that is your interest, our hands-on guide on how to use ChatGPT for coding covers the rival workflow, and our comparison of GitHub Copilot vs ChatGPT for coding shows where editor assistants fit. Claude Code plays in that same league, but from the terminal instead of the editor sidebar.

Claude Plans and Prices

Claude has a generous free tier and a ladder of paid plans. Here is the current shape of it; the official Claude pricing page always has the final numbers:

One honest warning about limits: Claude does not count simple messages. Usage is metered in rolling five-hour windows, with additional weekly caps on top. A long coding session with a big model can use your allowance much faster than casual chat, so heavy users should watch the usage indicator rather than being surprised mid-project.

Claude in Practice: Projects, Research and Long Documents

Features lists are easy to skim and easier to forget, so here is what the big ones feel like in a normal working week. A Project is where an ongoing job lives: say, your company's help-centre rewrite. You load the style guide, the old articles and a list of banned phrases once. Every chat inside that Project starts already knowing them, so you stop pasting the same instructions every morning. It sounds small, and it saves a surprising amount of patience.

Research mode is the other quiet star. Ask a normal chat a hard question and you get one confident answer. Ask Research mode and Claude goes away, reads across multiple sources, compares them and returns a structured report with citations you can check. For a student writing an essay or a founder sizing up a market, that difference, an answer versus a small investigation, is the whole value of the paid plans.

And then there are the long documents. Lawyers feed Claude contracts, authors feed it manuscripts, and developers feed it entire repositories. The 1 million token window means the model rarely says the file is too long, and the Constitutional training means it flags the odd clause on page 73 instead of cheerfully summarising the introduction. None of this is magic. It is simply a tool shaped, deliberately, around careful reading and careful writing.

Who Is Claude Best For?

Claude suits people whose work is mostly words and code: writers drafting and editing long pieces, researchers summarising piles of documents, students working through sources, and developers who want a careful pair programmer. Its tone is a feature in itself. Where some assistants answer every question like an overexcited salesperson, Claude is more like the colleague who reads the whole brief before speaking. For quick jokes and image tricks, rivals may feel livelier. For a 90-page contract summary at 11 pm, Claude is the one many professionals trust.

Frequently Asked Questions

Is Claude AI free?

Yes. The Free plan costs $0 and covers everyday use. Paid plans raise the limits and unlock features such as Projects, Research mode and Claude Code.

What is the best Claude model?

Fable 5.2 is the most capable, released on 9 November 2026. For daily work, Anthropic recommends Opus 5.5 as the default, with Sonnet 5.5 for balance and Haiku 5.5 for speed.

How much does Claude Pro cost?

Pro costs $20 per month, or $17 per month when billed yearly. Max is $100 per month and Ultra is $200 per month.

What is Constitutional AI?

It is Anthropic's training method, where the model is guided by a written set of principles and learns to critique and improve its own answers against them.

How big is Claude's context window?

The current model family shares a 1 million token context window, enough for very long documents or whole codebases in one conversation.

Conclusion

Claude has earned its place as the careful thinker of the AI assistant world: safety-led training, a huge context window, honest answers and serious coding tools, all wrapped in a calm personality. Start on the free plan with a genuinely long document you need to understand, and you will see the appeal in one session. If the work keeps growing, Pro is the natural next step, and the five-hour usage windows become the only number you need to watch.