OpenAI o3 vs Claude Opus 4

Both are frontier reasoning models. o3 edges ahead on hard math and code. Opus 4 edges ahead on writing and long-context analysis.

These are the two most capable models available as of mid-2025. Use them for your hardest problems. For everything else, use cheaper tiers.

	OpenAI o3	Claude Opus 4
Reasoning depth	Best-in-class on competition math (AIME) and code (SWE-bench).	Best-in-class on complex instruction following and long-context.
Context window	200K tokens.	200K tokens.
Pricing (input/output, $/1M)	$10 / $40 (varies by effort level).	$15 / $75.
Speed	Slow (extended thinking). Mini variant available.	Slow. Extended thinking available.
Writing quality	Very good.	Best in class for prose, nuance, and editing.
Coding	Top of most benchmarks.	Excellent. Better at explaining and reviewing than generating.
Safety / refusals	Less cautious than older o-series.	More cautious but convincible with context.

Pick OpenAI o3 when

Use o3 when: you have hard quantitative problems — math, competitive coding, science reasoning — or you need benchmark-grade performance.

Pick Claude Opus 4 when

Use Opus 4 when: writing quality, instruction nuance, or analyzing large documents is central to the task.

Bottom line

At $10-75 per million tokens, both models are expensive. Profile your task first on cheaper tiers (Sonnet, GPT-4o) and only escalate to these when you hit a measurable quality ceiling.

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