Model comparison
GPT-5.3 Codex vs o3-pro
GPT-5.3 Codex is the stronger model overall, scoring 45.8 to 42.9 on the Noometry Index.
Last verified . 2 shared benchmarks.
Summary
- They share 2 benchmarks with published results for both. GPT-5.3 Codex scores higher in 0 categories and o3-pro in 1 category; one gap is clear of the uncertainty.
- The widest gap is in coding, where o3-pro leads 55.5 to 48.6.
- The biggest single-benchmark swing is WeirdML: 79.3% for GPT-5.3 Codex and 58.2% for o3-pro.
- GPT-5.3 Codex is cheaper at $1.75 / $14 per million input/output tokens, against $20 / $80 for o3-pro.
- GPT-5.3 Codex accepts more context: 400K tokens versus 200K.
Side by side
| GPT-5.3 Codex | o3-pro | |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 45.8 | 42.9 |
| Released | 2026-02-05 | 2025-06-10 |
| Weights | Proprietary | Proprietary |
| Context window | 400K | 200K |
| Max output | 128K | 100K |
| Input $ / M tokens | $1.75 | $20 |
| Output $ / M tokens | $14 | $80 |
| Results tracked | 8 | 12 |
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Category by category
Coding o3-pro leads
GPT-5.3 Codex: 48.6 (#56), o3-pro: 55.5 (#24)
| Benchmark | GPT-5.3 Codex | o3-pro |
|---|---|---|
| WeirdML | 79.3% | 58.2% |
| SWE-bench Verified | 74.8% | — |
| Aider Polyglot | — | 84.9% |
| LMArena WebDev | 1409 | — |
| ALE-Bench | 1,655 | — |
Agentic & Tool Use Not comparable
GPT-5.3 Codex: 48.0 (#9), o3-pro: —
| Benchmark | GPT-5.3 Codex | o3-pro |
|---|---|---|
| Terminal-Bench | 78.4% | — |
| METR Time Horizons | 74.5% | — |
| Vending-Bench 2 | 5,940 | — |
Reasoning Not comparable
GPT-5.3 Codex: —, o3-pro: 23.8 (#171)
| Benchmark | GPT-5.3 Codex | o3-pro |
|---|---|---|
| Epoch Capabilities Index | 156.77 | 147.42 |
| ARC-AGI-2 | — | 4.9% |
| Kagi LLM Benchmark | — | 72.1% |
| ARC-AGI-1 | — | 59.3% |
| DTBench | — | 86.9% |
| LMCA | — | 38.5% |
Knowledge Not comparable
GPT-5.3 Codex: —, o3-pro: 29.5 (#238)
| Benchmark | GPT-5.3 Codex | o3-pro |
|---|---|---|
| Confabulations | — | 14.2% |
| Vectara Hallucination Rate | — | 23.3% |
Long Context Not comparable
GPT-5.3 Codex: —, o3-pro: 72.2 (#1)
| Benchmark | GPT-5.3 Codex | o3-pro |
|---|---|---|
| Fiction.LiveBench | — | 97.2% |
Writing & Preference Not comparable
GPT-5.3 Codex: —, o3-pro: 57.1 (#133)
| Benchmark | GPT-5.3 Codex | o3-pro |
|---|---|---|
| Short-Story Creative Writing | — | 84.4% |
Frequently asked questions
Is GPT-5.3 Codex better than o3-pro?
GPT-5.3 Codex is the stronger model overall, scoring 45.8 to 42.9 on the Noometry Index.
Which is cheaper, GPT-5.3 Codex or o3-pro?
GPT-5.3 Codex is cheaper. It lists at $1.75 per million input tokens and $14 per million output tokens; o3-pro lists at $20 and $80.
Is GPT-5.3 Codex or o3-pro better for coding?
o3-pro scores higher on coding benchmarks: 55.5 versus 48.6 in the Noometry coding category.
Which has the bigger context window?
GPT-5.3 Codex does, with 400K tokens against 200K.
How many benchmarks do GPT-5.3 Codex and o3-pro share?
2 benchmarks have published results for both models. GPT-5.3 Codex has 8 scored results on Noometry and o3-pro has 12.