Side-by-side benchmark comparison across agentic, coding, multimodal, knowledge, reasoning, and math workflows.
GPT-5.3 Codex has the cleaner overall profile here, landing at 89 versus 87. It is a real lead, but still close enough that category-level strengths matter more than the headline number.
GPT-5.3 Codex's sharpest advantage is in coding, where it averages 87.3 against 78.7. The single biggest benchmark swing on the page is LiveCodeBench, 85 to 75. GPT-5.3 Instant does hit back in multimodal & grounded, so the answer changes if that is the part of the workload you care about most.
GPT-5.3 Instant is also the more expensive model on tokens at $1.75 input / $14.00 output per 1M tokens, versus $2.50 input / $10.00 output per 1M tokens for GPT-5.3 Codex. GPT-5.3 Codex gives you the larger context window at 400K, compared with 128K for GPT-5.3 Instant.
Pick GPT-5.3 Codex if you want the stronger benchmark profile. GPT-5.3 Instant only becomes the better choice if multimodal & grounded is the priority.
GPT-5.3 Codex
88.1
GPT-5.3 Instant
82.9
GPT-5.3 Codex
87.3
GPT-5.3 Instant
78.7
GPT-5.3 Codex
91.3
GPT-5.3 Instant
95
GPT-5.3 Codex
93.7
GPT-5.3 Instant
94.2
GPT-5.3 Codex
80.3
GPT-5.3 Instant
80.8
GPT-5.3 Codex
93
GPT-5.3 Instant
96
GPT-5.3 Codex
92.8
GPT-5.3 Instant
93.4
GPT-5.3 Codex
97.7
GPT-5.3 Instant
97.2
GPT-5.3 Codex is ahead overall, 89 to 87. The biggest single separator in this matchup is LiveCodeBench, where the scores are 85 and 75.
GPT-5.3 Instant has the edge for knowledge tasks in this comparison, averaging 80.8 versus 80.3. Inside this category, FrontierScience is the benchmark that creates the most daylight between them.
GPT-5.3 Codex has the edge for coding in this comparison, averaging 87.3 versus 78.7. Inside this category, LiveCodeBench is the benchmark that creates the most daylight between them.
GPT-5.3 Codex has the edge for math in this comparison, averaging 97.7 versus 97.2. Inside this category, MATH-500 is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for reasoning in this comparison, averaging 94.2 versus 93.7. Inside this category, SimpleQA is the benchmark that creates the most daylight between them.
GPT-5.3 Codex has the edge for agentic tasks in this comparison, averaging 88.1 versus 82.9. Inside this category, BrowseComp is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for multimodal and grounded tasks in this comparison, averaging 95 versus 91.3. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for instruction following in this comparison, averaging 96 versus 93. Inside this category, IFEval is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for multilingual tasks in this comparison, averaging 93.4 versus 92.8. Inside this category, MMLU-ProX is the benchmark that creates the most daylight between them.
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