GPT-5.3 Instant vs o3-pro

Side-by-side benchmark comparison across agentic, coding, multimodal, knowledge, reasoning, and math workflows.

GPT-5.3 Instant is clearly ahead on the aggregate, 87 to 71. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

GPT-5.3 Instant's sharpest advantage is in coding, where it averages 78.7 against 49.2. The single biggest benchmark swing on the page is LiveCodeBench, 75 to 44.

o3-pro gives you the larger context window at 200K, compared with 128K for GPT-5.3 Instant.

Quick Verdict

Pick GPT-5.3 Instant if you want the stronger benchmark profile. o3-pro only becomes the better choice if you need the larger 200K context window.

Agentic

GPT-5.3 Instant

GPT-5.3 Instant

82.9

o3-pro

70.4

86
Terminal-Bench 2.0
69
82
BrowseComp
76
80
OSWorld-Verified
68

Coding

GPT-5.3 Instant

GPT-5.3 Instant

78.7

o3-pro

49.2

88
HumanEval
80
76
SWE-bench Verified
46
75
LiveCodeBench
44
83
SWE-bench Pro
55

Multimodal & Grounded

GPT-5.3 Instant

GPT-5.3 Instant

95

o3-pro

74.1

95
MMMU-Pro
70
95
OfficeQA Pro
79

Reasoning

GPT-5.3 Instant

GPT-5.3 Instant

94.2

o3-pro

83.6

96
SimpleQA
86
94
MuSR
84
97
BBH
89
92
LongBench v2
81
94
MRCRv2
81

Knowledge

GPT-5.3 Instant

GPT-5.3 Instant

80.8

o3-pro

67.1

99
MMLU
88
98
GPQA
89
96
SuperGPQA
87
94
OpenBookQA
85
89
MMLU-Pro
75
44
HLE
26
92
FrontierScience
77

Instruction Following

GPT-5.3 Instant

GPT-5.3 Instant

96

o3-pro

82

96
IFEval
82

Multilingual

GPT-5.3 Instant

GPT-5.3 Instant

93.4

o3-pro

81.1

96
MGSM
83
92
MMLU-ProX
80

Mathematics

GPT-5.3 Instant

GPT-5.3 Instant

97.2

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
98
MATH-500
89

Frequently Asked Questions

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

GPT-5.3 Instant is ahead overall, 87 to 71. The biggest single separator in this matchup is LiveCodeBench, where the scores are 75 and 44.

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

GPT-5.3 Instant has the edge for knowledge tasks in this comparison, averaging 80.8 versus 67.1. Inside this category, HLE is the benchmark that creates the most daylight between them.

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

GPT-5.3 Instant has the edge for coding in this comparison, averaging 78.7 versus 49.2. Inside this category, LiveCodeBench is the benchmark that creates the most daylight between them.

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

GPT-5.3 Instant has the edge for math in this comparison, averaging 97.2 versus 89. Inside this category, AIME 2023 is the benchmark that creates the most daylight between them.

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

GPT-5.3 Instant has the edge for reasoning in this comparison, averaging 94.2 versus 83.6. Inside this category, MRCRv2 is the benchmark that creates the most daylight between them.

Which is better for agentic tasks, GPT-5.3 Instant or o3-pro?

GPT-5.3 Instant has the edge for agentic tasks in this comparison, averaging 82.9 versus 70.4. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.

Which is better for multimodal and grounded tasks, GPT-5.3 Instant or o3-pro?

GPT-5.3 Instant has the edge for multimodal and grounded tasks in this comparison, averaging 95 versus 74.1. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.

Which is better for instruction following, GPT-5.3 Instant or o3-pro?

GPT-5.3 Instant has the edge for instruction following in this comparison, averaging 96 versus 82. Inside this category, IFEval is the benchmark that creates the most daylight between them.

Which is better for multilingual tasks, GPT-5.3 Instant or o3-pro?

GPT-5.3 Instant has the edge for multilingual tasks in this comparison, averaging 93.4 versus 81.1. Inside this category, MGSM is the benchmark that creates the most daylight between them.

Last updated: March 12, 2026

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