GPT-5.3 Codex vs GPT-5 (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 72 (13 point difference).GPT-5.3 Codex wins 4 out of 4 categories.

Knowledge

GPT-5.3 Codex

GPT-5.3 Codex

96

GPT-5 (high)

90

99
MMLU
93
97
GPQA
91
95
SuperGPQA
89
93
OpenBookQA
87

Coding

GPT-5.3 Codex

GPT-5.3 Codex

95

GPT-5 (high)

85

95
HumanEval
85

Mathematics

GPT-5.3 Codex

GPT-5.3 Codex

97.1

GPT-5 (high)

94

99
AIME 2023
95
99
AIME 2024
97
98
AIME 2025
96
95
HMMT Feb 2023
91
97
HMMT Feb 2024
93
96
HMMT Feb 2025
92
96
BRUMO 2025
94

Reasoning

GPT-5.3 Codex

GPT-5.3 Codex

94

GPT-5 (high)

88

95
SimpleQA
89
93
MuSR
87

Frequently Asked Questions

Which is better, GPT-5.3 Codex or GPT-5 (high)?

GPT-5.3 Codex scores higher overall with 85 vs 72, a difference of 13 points across all benchmarks.

Which is better for knowledge tasks, GPT-5.3 Codex or GPT-5 (high)?

GPT-5.3 Codex leads in knowledge tasks with an average score of 96 vs 90.

Which is better for coding, GPT-5.3 Codex or GPT-5 (high)?

GPT-5.3 Codex leads in coding with an average score of 95 vs 85.

Which is better for math, GPT-5.3 Codex or GPT-5 (high)?

GPT-5.3 Codex leads in math with an average score of 97.1 vs 94.

Which is better for reasoning, GPT-5.3 Codex or GPT-5 (high)?

GPT-5.3 Codex leads in reasoning with an average score of 94 vs 88.