Free Claude 3.5 Sonnet API

Claude 3.5 Sonnet remains one of the most useful Anthropic models for coding, analysis, tool use, and careful writing. It is older than the latest Sonnet line, but still a practical free API target when you want Claude-style output without paying upfront.

Why choose it?

• Coding strength: strong at refactors, explanations, and agentic development loops.
• Long context: useful for reading larger files and documentation.
• Low-friction free access: Vercel AI Gateway monthly credits let you test it without bringing an Anthropic key.

Free access option

• Vercel AI Gateway: call anthropic/claude-3.5-sonnet through an OpenAI-compatible endpoint with monthly credits and no credit card required to start.

Choose Claude 3.5 Sonnet for coding-heavy prototypes, then compare the newer Claude Sonnet and Opus alternatives if you need higher capability.