What's the difference between Claude Sonnet 4 and Sonnet 3.7?
Quick answer: Sonnet 4 is newer and stronger overall, especially on long-form writing and complex reasoning. Sonnet 3.7 is faster and cheaper, and excellent for everyday tasks.
Anthropic ships Sonnet versions roughly every 4-8 months. The lineage today on AskAI.free:
- Sonnet 3.5 — June 2024. Available on the free tier. Still very capable for everyday writing.
- Sonnet 3.7 — early 2025. Better instruction-following and faster than 3.5. Roughly half the token cost of Sonnet 4.
- Sonnet 4 — Anthropic's flagship Sonnet. Strongest at long-form writing, complex reasoning, multi-file code. Costs 4× more tokens per question.
Practical advice: use 3.7 as your daily driver and reach for Sonnet 4 when you have a hard, important task that's worth a few extra cents.
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