Question 1

What is Claude 4 Sonnet?

Accepted Answer

Claude 4 Sonnet is a large language model from Anthropic, released on 10 February 2026. The Anthropic sweet spot — Opus-class coding at a fraction of the price.

Question 2

When was Claude 4 Sonnet released?

Accepted Answer

Claude 4 Sonnet was released by Anthropic on 10 February 2026.

Question 3

How much does Claude 4 Sonnet cost?

Accepted Answer

Claude 4 Sonnet costs $3.00 per 1 million input tokens and $15.00 per 1 million output tokens via Anthropic’s API. At a typical 3:1 input/output ratio the blended cost works out to about $6.00 per 1M tokens.

Question 4

How smart is Claude 4 Sonnet?

Accepted Answer

Claude 4 Sonnet scores 75 out of 100 on our intelligence index — a strong production-tier composite of MMLU, MMLU Pro, GPQA, MATH and HumanEval benchmark scores. That places it #5 of 22 language models we track.

Question 5

What is the context window of Claude 4 Sonnet?

Accepted Answer

Claude 4 Sonnet has a 500k-token context window — roughly 375,000 words of text. That’s what you can fit into a single request (your prompt plus all uploaded documents and the model’s response combined).

Question 6

What is Claude 4 Sonnet best for?

Accepted Answer

Claude 4 Sonnet is most useful for production coding tools, long-context rag and tool use. Its key strengths are best $/humaneval ratio, fast and 500k context.

Question 7

How fast is Claude 4 Sonnet?

Accepted Answer

Claude 4 Sonnet generates around 95 output tokens per second with a typical time-to-first-token of 850 ms on the major API providers. Reasoning models that "think" before answering will appear slower on tokens-per-second since they spend time on internal chain-of-thought.

Question 8

Is Claude 4 Sonnet better than Claude 4 Opus?

Accepted Answer

Claude 4 Opus scores higher on our intelligence index (81 vs 75), so on the hardest tasks Claude 4 Opus typically wins. Claude 4 Sonnet can still be the better pick on price, latency or specific capabilities. See our full Claude 4 Sonnet vs Claude 4 Opus comparison at /ai-models/compare/claude-4-opus-vs-claude-4-sonnet/.

Question 9

What is the best alternative to Claude 4 Sonnet?

Accepted Answer

The closest alternatives to Claude 4 Sonnet are Claude 4 Opus, Claude 3.5 Sonnet and GPT-5.5. Each shares most of Claude 4 Sonnet’s use-cases — pick by price, context window or specific capability rather than headline intelligence.

Question 10

Is Claude 4 Sonnet open source?

Accepted Answer

No. Claude 4 Sonnet is proprietary — the weights are not released. Access is via Anthropic’s own API and partner platforms. For open-weights alternatives in the same tier, see our open-source AI models page.

Question 11

Can I use Claude 4 Sonnet for free?

Accepted Answer

Anthropic offers a free tier of Claude 4 Sonnet through claude.ai with daily usage limits. The API is paid, though new accounts get a small starting credit. Some Slack, Notion and developer-tool integrations also bundle Claude usage without separate billing.

Claude 4 Sonnet

At a glance

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