benchlm.ai

Claude Opus 4.5 vs GPT-5.3 Codex

Side-by-side benchmark comparison across knowledge, coding, math, and reasoning.

Quick Verdict

GPT-5.3 Codex wins overall with a score of 85 vs 79 (6 point difference).GPT-5.3 Codex wins 1 out of 4 categories.

Claude Opus 4.5

CreatorAnthropic
TypeProprietary
Context200K
Score79

GPT-5.3 Codex

CreatorOpenAI
TypeProprietary
Context400K
Score85

Knowledge

Tie

Claude Opus 4.5

96

GPT-5.3 Codex

96

99
MMLU
99
97
GPQA
97
95
SuperGPQA
95
93
OpenBookQA
93

Coding

GPT-5.3 Codex

Claude Opus 4.5

91

GPT-5.3 Codex

95

91
HumanEval
95

Mathematics

Tie

Claude Opus 4.5

97.1

GPT-5.3 Codex

97.1

99
AIME 2023
99
99
AIME 2024
99
98
AIME 2025
98
95
HMMT Feb 2023
95
97
HMMT Feb 2024
97
96
HMMT Feb 2025
96
96
BRUMO 2025
96

Reasoning

Tie

Claude Opus 4.5

94

GPT-5.3 Codex

94

95
SimpleQA
95
93
MuSR
93

Frequently Asked Questions

Which is better, Claude Opus 4.5 or GPT-5.3 Codex?

GPT-5.3 Codex scores higher overall with 85 vs 79, a difference of 6 points across all benchmarks.

Which is better for knowledge tasks, Claude Opus 4.5 or GPT-5.3 Codex?

Claude Opus 4.5 and GPT-5.3 Codex are tied for knowledge tasks with average scores of 96.

Which is better for coding, Claude Opus 4.5 or GPT-5.3 Codex?

GPT-5.3 Codex leads in coding with an average score of 95 vs 91.

Which is better for math, Claude Opus 4.5 or GPT-5.3 Codex?

Claude Opus 4.5 and GPT-5.3 Codex are tied for math with average scores of 97.1.

Which is better for reasoning, Claude Opus 4.5 or GPT-5.3 Codex?

Claude Opus 4.5 and GPT-5.3 Codex are tied for reasoning with average scores of 94.

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