What is the difference between Claude Sonnet and Claude Opus?

Claude Opus is Anthropic's most powerful and intelligent model — it is designed for complex reasoning, nuanced writing, deep analysis, and difficult coding tasks. It is slower and more expensive to run. Claude Sonnet sits in the middle: it is significantly faster than Opus and much cheaper, while still being very capable for the vast majority of tasks. For most day-to-day use cases, Sonnet is the better choice.

Think of it like this — use Sonnet for everyday tasks like drafting emails, summarizing documents, writing code, and answering questions. Switch to Opus when you need the absolute best quality on something complex, like reviewing a legal document, solving a hard algorithmic problem, or writing a detailed research report. Claude Pro subscribers can switch between both models inside claude.ai.