benchlm.ai

Gemini 3 Flash 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 58 (27 point difference).GPT-5.3 Codex wins 4 out of 4 categories.

Gemini 3 Flash

CreatorGoogle
TypeProprietary
Context1M
Score58

GPT-5.3 Codex

CreatorOpenAI
TypeProprietary
Context400K
Score85

Knowledge

GPT-5.3 Codex

Gemini 3 Flash

67.8

GPT-5.3 Codex

96

70
MMLU
99
69
GPQA
97
67
SuperGPQA
95
65
OpenBookQA
93

Coding

GPT-5.3 Codex

Gemini 3 Flash

62

GPT-5.3 Codex

95

62
HumanEval
95

Mathematics

GPT-5.3 Codex

Gemini 3 Flash

69

GPT-5.3 Codex

97.1

70
AIME 2023
99
72
AIME 2024
99
71
AIME 2025
98
66
HMMT Feb 2023
95
68
HMMT Feb 2024
97
67
HMMT Feb 2025
96
69
BRUMO 2025
96

Reasoning

GPT-5.3 Codex

Gemini 3 Flash

66

GPT-5.3 Codex

94

67
SimpleQA
95
65
MuSR
93

Frequently Asked Questions

Which is better, Gemini 3 Flash or GPT-5.3 Codex?

GPT-5.3 Codex scores higher overall with 85 vs 58, a difference of 27 points across all benchmarks.

Which is better for knowledge tasks, Gemini 3 Flash or GPT-5.3 Codex?

GPT-5.3 Codex leads in knowledge tasks with an average score of 96 vs 67.8.

Which is better for coding, Gemini 3 Flash or GPT-5.3 Codex?

GPT-5.3 Codex leads in coding with an average score of 95 vs 62.

Which is better for math, Gemini 3 Flash or GPT-5.3 Codex?

GPT-5.3 Codex leads in math with an average score of 97.1 vs 69.

Which is better for reasoning, Gemini 3 Flash or GPT-5.3 Codex?

GPT-5.3 Codex leads in reasoning with an average score of 94 vs 66.

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