Side-by-side benchmark comparison across knowledge, coding, math, and reasoning.
GPT-5.3 Codex is clearly ahead on the aggregate, 92 to 31. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5.3 Codex's sharpest advantage is in knowledge, where it averages 86.3 against 71.2. The single biggest benchmark swing on the page is GPQA, 97 to 71.2.
GPT-5.3 Codex is also the more expensive model on tokens at $2.50 input / $10.00 output per 1M tokens, versus $0.05 input / $0.40 output per 1M tokens for GPT-5 nano. That is roughly 25.0x on output cost alone.
Pick GPT-5.3 Codex if you want the stronger benchmark profile. GPT-5 nano only becomes the better choice if you want the cheaper token bill.
GPT-5.3 Codex
86.3
GPT-5 nano
71.2
GPT-5.3 Codex
97.4
GPT-5 nano
85.2
GPT-5.3 Codex is ahead overall, 92 to 31. The biggest single separator in this matchup is GPQA, where the scores are 97 and 71.2.
GPT-5.3 Codex has the edge for knowledge tasks in this comparison, averaging 86.3 versus 71.2. Inside this category, GPQA is the benchmark that creates the most daylight between them.
GPT-5.3 Codex has the edge for math in this comparison, averaging 97.4 versus 85.2. Inside this category, AIME 2025 is the benchmark that creates the most daylight between them.
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