What's the best free AI for writing and debugging code?
Quick answer: On the free tier, Claude Sonnet 3.5 is best for explaining and refactoring; ChatGPT 4o is fastest for snippet-level help. Both are strong enough for daily coding.
On the free tier:
- Claude Sonnet 3.5 — best for "read this code and tell me what's wrong" or "refactor this function". Clearer explanations.
- ChatGPT 4o — fastest for "how do I do X in Python" type questions and bug-fix snippets.
If your codebase is more than a few hundred lines, free-tier models start to struggle with context. Upgrade to Pro for Claude Sonnet 4 — its larger context window and stronger reasoning make it a noticeably better pair-programmer.
Pro tip: paste error messages verbatim, not paraphrased. The exact stack trace is the most useful information you can give the AI.
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