benchlm.ai

GPT-5.3 Codex vs o4-mini (high)

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 65 (20 point difference).GPT-5.3 Codex wins 4 out of 4 categories.

GPT-5.3 Codex

CreatorOpenAI
TypeProprietary
Context400K
Score85

o4-mini (high)

CreatorOpenAI
TypeProprietary
Context200K
Score65

Knowledge

GPT-5.3 Codex

GPT-5.3 Codex

96

o4-mini (high)

80.5

99
MMLU
82
97
GPQA
82
95
SuperGPQA
80
93
OpenBookQA
78

Coding

GPT-5.3 Codex

GPT-5.3 Codex

95

o4-mini (high)

74

95
HumanEval
74

Mathematics

GPT-5.3 Codex

GPT-5.3 Codex

97.1

o4-mini (high)

82

99
AIME 2023
83
99
AIME 2024
85
98
AIME 2025
84
95
HMMT Feb 2023
79
97
HMMT Feb 2024
81
96
HMMT Feb 2025
80
96
BRUMO 2025
82

Reasoning

GPT-5.3 Codex

GPT-5.3 Codex

94

o4-mini (high)

79

95
SimpleQA
80
93
MuSR
78

Frequently Asked Questions

Which is better, GPT-5.3 Codex or o4-mini (high)?

GPT-5.3 Codex scores higher overall with 85 vs 65, a difference of 20 points across all benchmarks.

Which is better for knowledge tasks, GPT-5.3 Codex or o4-mini (high)?

GPT-5.3 Codex leads in knowledge tasks with an average score of 96 vs 80.5.

Which is better for coding, GPT-5.3 Codex or o4-mini (high)?

GPT-5.3 Codex leads in coding with an average score of 95 vs 74.

Which is better for math, GPT-5.3 Codex or o4-mini (high)?

GPT-5.3 Codex leads in math with an average score of 97.1 vs 82.

Which is better for reasoning, GPT-5.3 Codex or o4-mini (high)?

GPT-5.3 Codex leads in reasoning with an average score of 94 vs 79.

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