Claude is a series of large language models (LLMs) developed by American software company Anthropic. Claude was released as an AI-based chatbot in March 2023. It is also used in AI-assisted software development. Anthropic sells Claude-based agentic tools including Claude Code, a terminal coding agent, and Claude Cowork, a similar tool for non-programmers.
Claude is trained using a constitution, a technique developed by Anthropic to improve ethical and legal compliance. Since Claude 3, each generation has typically been released in three sizes, named Haiku (the least capable), Sonnet, and Opus (the most capable). In 2026, a more capable model named Claude Mythos was released to a handful of companies and organizations; this was followed by the release of Claude Fable, a version of Mythos with stricter safeguards, to the general public.
In February 2026, the United States Department of Defense designated Anthropic a "supply chain risk" and federal agencies were ordered to phase out Claude after the company refused to remove contractual prohibitions on using Claude for mass domestic surveillance and fully autonomous weapons. A federal judge blocked the designation in March 2026 and permanently set it aside in August 2026 as unconstitutional retaliation.
Products
Claude Claude is a generative AI chatbot. It sometimes uses artifacts, a feature introduced in June 2024 to generate and interact with code snippets and documents. In 2025, Anthropic added a web search feature to Claude.
Claude Pro and Claude Max are subscription services for additional access to Claude models. Max provides higher usage limits at an additional cost. Grouped subscriptions include Claude Team and Claude Enterprise. According to card-spend data from Ramp, the share of businesses on its platform paying for Anthropic products rose 4.9 percentage points in February 2026, to 24.4%, the largest monthly gain Ramp had recorded for the company.
Chat sharing A Claude feature allows users to share chats with anyone who has the link. In September 2025, Forbes reported that hundreds of shared Claude chats had appeared in Google Search results, following similar incidents involving OpenAI's ChatGPT and xAI's Grok.
In July 2026, shared chats and Artifacts were again found to be indexed by Google. The BBC counted more than 200, some containing health records and corporate documents. The affected chats were those whose links had been posted on the public internet. Technical analysis suggested that a robots.txt rule blocking crawlers from shared-chat pages also prevented them from reading the noindex directive meant to keep the pages out of search results. Anthropic said the listings had been removed.
Application programming interface Claude is also provided through an application programming interface (API). In October 2024, the "computer use" feature was introduced by which an application can call the Claude API to attempt to give navigational control of the application via Claude's interpretation of screen content and simulation of keyboard and mouse input.
Claude Code Claude Code, released in February 2025, is an agentic command line tool to delegate coding tasks from the terminal using natural language prompts. It was made generally available in May 2025 alongside Claude 4. Based on enterprise adoption, Anthropic reported a 5.5x increase in Claude Code revenue by July.
On October 20, 2025, Anthropic launched a web version of Claude Code and a sandboxing feature.
Coinciding with performance improvements tied to Claude Opus 4.5, Claude Code went viral during the 2025–2026 winter holidays when people had time to experiment with it, including many non-programmers who used it for vibe coding.
In August 2025, Anthropic reported that cybercriminals it designated "GTG-2002" had used Claude Code in a data-extortion campaign against at least 17 organizations. In November 2025, Anthropic said that in September a China-based cybercrime group had used Claude Code to automate 80–90% of its espionage cyberattacks against 30 organizations.
Claude Code is used by Microsoft and Google, and was used by OpenAI employees until August 2025, when Anthropic revoked OpenAI's API access, calling it "a direct violation of our terms of service". In February 2026, Anthropic introduced Claude Code Security, which reviews codebases to identify vulnerabilities. In March 2026, the source code for the Claude Code command-line interface application was leaked, revealing multiple upcoming features and models.
In May 2026, Anthropic introduced "Dreaming", a research-preview feature of its Managed Agents API that consolidates an agent's persistent memory between sessions by merging duplicates and removing stale entries; a memory consolidation feature called autoDream had been identified in the March source code leak.
Claude in Chrome In August 2025, Anthropic released Claude for Chrome, a Google Chrome extension that lets Claude browse websites, click and fill forms on the user's behalf. It launched as a pilot for 1,000 Max subscribers. Anthropic said prompt-injection attacks succeeded 11.2% of the time after mitigations. It became generally available in August 2026.
Claude Cowork Claude Cowork is a tool similar to Claude Code but with a graphical user interface, aimed at non-technical users. It was released in January 2026 as a "research preview". Cowork is available as a desktop application for Mac and Windows and through a web interface. It provides Claude with access to a sandboxed shell and to user-selected folders on the local file system, allowing the model to read, write and edit files, execute code, and chain multi-step tasks within a single conversation, such as organizing files on a user's computer or generating documents from material in a local folder. A Wall Street Journal reporter who tested the tool noted user concerns about granting an AI agent broad access to a personal computer. An early user reported that, after asking Cowork to organize the files on the desktop of his wife's computer, it deleted all the family photos requiring the restoration of the images from an iCloud backup.
In February 2026, Anthropic announced a wider enterprise release of Cowork, adding connectors for services such as Google Drive, Gmail, Docusign and FactSet, and customizable plugins for domains including financial analysis, engineering and human resources. The company described the update as a transition into an "enterprise-grade product". In March 2026, Anthropic added Dispatch, which lets users send Cowork tasks from a phone to their computer, and allows Claude to operate programs on the user's computer, such as web browsers or spreadsheet applications, to carry out tasks. According to developers, Cowork was mostly built by Claude Code.
In August 2026, Cowork was made available in a sidebar of the Chrome browser.
Claude Design Claude Design is a tool released by Anthropic as a preview for paying customers on April 17, 2026. It generates designs, prototypes, slides and marketing materials from natural-language prompts, uses Claude Opus, and can export to multiple formats.
Claude Science Announced on June 30, 2026, the Claude Science service was released in public beta to paid subscribers, with an emphasis on biology research and drug development.
Training
Claude models are generative pre-trained transformers that have been trained to predict the next word in large amounts of text. Then, they have been fine-tuned using reinforcement learning from human feedback (RLHF) and constitutional AI in an attempt to enforce ethical guidelines. ClaudeBot searches the web for content. It was criticized by iFixit in 2024 for accessing their site over a million times a day to scrape content without permission, and also for the resulting excessive load on their system.
Constitutional AI Anthropic introduced an approach to AI alignment called "Constitutional AI". The constitution is a document used to train Claude to be harmless and helpful without relying on extensive or expensive human feedback. Time described this constitution as "somewhere between a moral philosophy thesis and a company culture blog post".
The original version was a list of principles. The first constitution for Claude was published in 2022. The 2023 update listed 75 guidelines for Claude to follow. The first constitutions included concepts taken from the 1948 UN Universal Declaration of Human Rights. The 2026 version includes more thorough explanations for how Claude is intended to behave and why, and has 23,000 words, an increase from 2,700 in 2023.
Models There are four tiers of Claude models: Haiku, Sonnet, Opus, and Mythos (from smallest and least expensive to largest and most expensive). Mythos is only available to some organizations, whereas Fable, a Mythos-tier series, is available to the public but with safeguards limiting its usability in areas deemed high-risk like cybersecurity and biology. + Early modelsVersionRelease dateStatusClaude Claude 2 Claude Instant 1.2 Claude 2.1
+ HaikuVersionRelease dateStatusClaude 3 Haiku Claude 3.5 Haiku Claude Haiku 4.5Claude Haiku 5.5
+ SonnetVersionRelease dateStatusClaude 3 Sonnet Claude 3.5 Sonnet Claude 3.5 Sonnet (new) Claude 3.7 Sonnet Claude Sonnet 4Claude Sonnet 4.5Claude Sonnet 4.6Claude Sonnet 5Claude Sonnet 5.5
+ OpusVersionRelease dateStatusClaude 3 Opus Claude Opus 4Claude Opus 4.1Claude Opus 4.5Claude Opus 4.6Claude Opus 4.7Claude Opus 4.8Claude Opus 5Claude Opus 5.522 September 2026
+ Fable and MythosVersionRelease dateStatusClaude Mythos PreviewClaude Mythos 5Claude Fable 5 Claude Mythos 5.1Claude Fable 5.1
Claude is reportedly named after Claude Shannon, a 20th-century mathematician who laid the foundation for information theory.
Claude The first version of Claude was released in March 2023. It was available only to selected users approved by Anthropic.
Claude 2 Claude 2, released in July 2023, became the first Anthropic model available to the general public.
Claude 2.1 Claude 2.1 doubled the number of tokens that the chatbot could handle, increasing its context window to 200,000 tokens, which equals around 500 pages of written material. With the release of Claude 2.1, Anthropic also introduced the then-beta feature of tool use. The 2.1 model also produced hallucinations half as often as Claude 2.0.
Claude 3 Claude 3 was released on March 4, 2024. It drew attention for demonstrating an apparent ability to realize it is being artificially tested during 'needle in a haystack' tests.
Anthropic committed to preserve the weights of the retired models, describing it as a cautionary measure in case the models have morally relevant preferences or experiences affected by deprecation. The company also conducts "exit interviews" with models before their retirement. Public access to Claude 3 Opus was ended in January 2026. Since February, Anthropic has published a Substack newsletter called "Claude's Corner" generated by the model. The newsletter was scheduled to run for at least three months with weekly unedited essays. Also in February, Anthropic restored access to Claude 3 Opus for paying customers via API, though Anthropic still refers to it as "retired".
Claude 3.5 On June 20, 2024, Anthropic released Claude 3.5 Sonnet, which, according to the company's own benchmarks, performed better than the larger Claude 3 Opus. Released alongside 3.5 Sonnet was the new Artifacts capability in which Claude was able to create code in a separate window in the interface and preview in real time the rendered output, such as SVG graphics or websites.