Model comparison
GPT-5.1-Codex vs GPT-5.3 Codex
GPT-5.3 Codex is the stronger model overall, scoring 45.5 to 38.2 on the Noometry Index.
Last verified . 4 shared benchmarks.
Summary
- They share 4 benchmarks with published results for both. GPT-5.1-Codex scores higher in 0 categories and GPT-5.3 Codex in 2 categories; 2 gaps are clear of the uncertainty.
- The widest gap is in agentic & tool use, where GPT-5.3 Codex leads 47.8 to 37.8.
- The biggest single-benchmark swing is Terminal-Bench: 60.4% for GPT-5.1-Codex and 78.4% for GPT-5.3 Codex.
- GPT-5.1-Codex is cheaper at $1.25 / $10 per million input/output tokens, against $1.75 / $14 for GPT-5.3 Codex.
Side by side
| GPT-5.1-Codex | GPT-5.3 Codex | |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 38.2 | 45.5 |
| Released | 2025-11-12 | 2026-02-05 |
| Weights | Proprietary | Proprietary |
| Context window | 400K | 400K |
| Max output | 128K | 128K |
| Input $ / M tokens | $1.25 | $1.75 |
| Output $ / M tokens | $10 | $14 |
| Results tracked | 6 | 8 |
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Category by category
Coding GPT-5.3 Codex leads
GPT-5.1-Codex: 41.7 (#107), GPT-5.3 Codex: 48.5 (#51)
| Benchmark | GPT-5.1-Codex | GPT-5.3 Codex |
|---|---|---|
| LMArena WebDev | 1337 | 1408 |
| ALE-Bench | 1,245 | 1,655 |
| SWE-bench Verified | — | 74.8% |
| SWE-bench Verified (bash only) | 66% | — |
| WeirdML | — | 79.3% |
Agentic & Tool Use GPT-5.3 Codex leads
GPT-5.1-Codex: 37.8 (#32), GPT-5.3 Codex: 47.8 (#9)
| Benchmark | GPT-5.1-Codex | GPT-5.3 Codex |
|---|---|---|
| Terminal-Bench | 60.4% | 78.4% |
| METR Time Horizons | 70.8% | 74.5% |
| Vending-Bench 2 | — | 5,940 |
Reasoning Not comparable
GPT-5.1-Codex: —, GPT-5.3 Codex: —
| Benchmark | GPT-5.1-Codex | GPT-5.3 Codex |
|---|---|---|
| Epoch Capabilities Index | — | 156.84 |
Math Not comparable
GPT-5.1-Codex: 29.3 (#218), GPT-5.3 Codex: —
| Benchmark | GPT-5.1-Codex | GPT-5.3 Codex |
|---|---|---|
| ProofBench | 9% | — |
Frequently asked questions
Is GPT-5.1-Codex better than GPT-5.3 Codex?
GPT-5.3 Codex is the stronger model overall, scoring 45.5 to 38.2 on the Noometry Index.
Which is cheaper, GPT-5.1-Codex or GPT-5.3 Codex?
GPT-5.1-Codex is cheaper. It lists at $1.25 per million input tokens and $10 per million output tokens; GPT-5.3 Codex lists at $1.75 and $14.
Is GPT-5.1-Codex or GPT-5.3 Codex better for coding?
GPT-5.3 Codex scores higher on coding benchmarks: 48.5 versus 41.7 in the Noometry coding category.
Which has the bigger context window?
Both accept 400K tokens.
How many benchmarks do GPT-5.1-Codex and GPT-5.3 Codex share?
4 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and GPT-5.3 Codex has 8.