benchlm.ai

GPT-5.3 Codex vs Grok Code Fast 1

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 54 (31 point difference).GPT-5.3 Codex wins 4 out of 4 categories.

GPT-5.3 Codex

CreatorOpenAI
TypeProprietary
Context400K
Score85

Grok Code Fast 1

CreatorxAI
TypeProprietary
Context256K
Score54

Knowledge

GPT-5.3 Codex

GPT-5.3 Codex

96

Grok Code Fast 1

61.8

99
MMLU
64
97
GPQA
63
95
SuperGPQA
61
93
OpenBookQA
59

Coding

GPT-5.3 Codex

GPT-5.3 Codex

95

Grok Code Fast 1

60

95
HumanEval
60

Mathematics

GPT-5.3 Codex

GPT-5.3 Codex

97.1

Grok Code Fast 1

63

99
AIME 2023
64
99
AIME 2024
66
98
AIME 2025
65
95
HMMT Feb 2023
60
97
HMMT Feb 2024
62
96
HMMT Feb 2025
61
96
BRUMO 2025
63

Reasoning

GPT-5.3 Codex

GPT-5.3 Codex

94

Grok Code Fast 1

60

95
SimpleQA
61
93
MuSR
59

Frequently Asked Questions

Which is better, GPT-5.3 Codex or Grok Code Fast 1?

GPT-5.3 Codex scores higher overall with 85 vs 54, a difference of 31 points across all benchmarks.

Which is better for knowledge tasks, GPT-5.3 Codex or Grok Code Fast 1?

GPT-5.3 Codex leads in knowledge tasks with an average score of 96 vs 61.8.

Which is better for coding, GPT-5.3 Codex or Grok Code Fast 1?

GPT-5.3 Codex leads in coding with an average score of 95 vs 60.

Which is better for math, GPT-5.3 Codex or Grok Code Fast 1?

GPT-5.3 Codex leads in math with an average score of 97.1 vs 63.

Which is better for reasoning, GPT-5.3 Codex or Grok Code Fast 1?

GPT-5.3 Codex leads in reasoning with an average score of 94 vs 60.

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