benchlm.ai

GPT-5.3 Codex vs o3-pro

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 68 (17 point difference).GPT-5.3 Codex wins 4 out of 4 categories.

GPT-5.3 Codex

CreatorOpenAI
TypeProprietary
Context400K
Score85

o3-pro

CreatorOpenAI
TypeProprietary
Context200K
Score68

Knowledge

GPT-5.3 Codex

GPT-5.3 Codex

96

o3-pro

87.3

99
MMLU
88
97
GPQA
89
95
SuperGPQA
87
93
OpenBookQA
85

Coding

GPT-5.3 Codex

GPT-5.3 Codex

95

o3-pro

80

95
HumanEval
80

Mathematics

GPT-5.3 Codex

GPT-5.3 Codex

97.1

o3-pro

89

99
AIME 2023
90
99
AIME 2024
92
98
AIME 2025
91
95
HMMT Feb 2023
86
97
HMMT Feb 2024
88
96
HMMT Feb 2025
87
96
BRUMO 2025
89

Reasoning

GPT-5.3 Codex

GPT-5.3 Codex

94

o3-pro

85

95
SimpleQA
86
93
MuSR
84

Frequently Asked Questions

Which is better, GPT-5.3 Codex or o3-pro?

GPT-5.3 Codex scores higher overall with 85 vs 68, a difference of 17 points across all benchmarks.

Which is better for knowledge tasks, GPT-5.3 Codex or o3-pro?

GPT-5.3 Codex leads in knowledge tasks with an average score of 96 vs 87.3.

Which is better for coding, GPT-5.3 Codex or o3-pro?

GPT-5.3 Codex leads in coding with an average score of 95 vs 80.

Which is better for math, GPT-5.3 Codex or o3-pro?

GPT-5.3 Codex leads in math with an average score of 97.1 vs 89.

Which is better for reasoning, GPT-5.3 Codex or o3-pro?

GPT-5.3 Codex leads in reasoning with an average score of 94 vs 85.

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