Model comparison
GPT-5.1-Codex vs GPT-5.3 Chat
GPT-5.3 Chat is the stronger model overall, scoring 42.8 to 38.6 on the Noometry Index.
Last verified . 0 shared benchmarks.
Summary
- The widest gap is in math, where GPT-5.3 Chat leads 38.2 to 30.3.
- GPT-5.1-Codex is cheaper at $1.25 / $10 per million input/output tokens, against $1.75 / $14 for GPT-5.3 Chat.
- GPT-5.1-Codex accepts more context: 400K tokens versus 128K.
Side by side
| GPT-5.1-Codex | GPT-5.3 Chat | |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 38.6 | 42.8 |
| Released | 2025-11-12 | 2026-03-03 |
| Weights | Proprietary | Proprietary |
| Context window | 400K | 128K |
| Max output | 128K | 16K |
| Input $ / M tokens | $1.25 | $1.75 |
| Output $ / M tokens | $10 | $14 |
| Results tracked | 6 | 18 |
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Category by category
Coding Too close to call
GPT-5.1-Codex: 41.9 (#116), GPT-5.3 Chat: 41.4 (#124)
| Benchmark | GPT-5.1-Codex | GPT-5.3 Chat |
|---|---|---|
| SWE-bench Verified (bash only) | 66% | — |
| LMArena WebDev | 1337 | — |
| LMArena Coding | — | 1408 |
| ALE-Bench | 1,245 | — |
Agentic & Tool Use Not comparable
GPT-5.1-Codex: 38.0 (#33), GPT-5.3 Chat: —
| Benchmark | GPT-5.1-Codex | GPT-5.3 Chat |
|---|---|---|
| Terminal-Bench | 60.4% | — |
| METR Time Horizons | 70.8% | — |
Reasoning Not comparable
GPT-5.1-Codex: —, GPT-5.3 Chat: 28.5 (#102)
| Benchmark | GPT-5.1-Codex | GPT-5.3 Chat |
|---|---|---|
| LMArena Hard Prompts | — | 1399 |
Math GPT-5.3 Chat leads
GPT-5.1-Codex: 30.3 (#235), GPT-5.3 Chat: 38.2 (#142)
| Benchmark | GPT-5.1-Codex | GPT-5.3 Chat |
|---|---|---|
| ProofBench | 9% | — |
| LMArena Math | — | 1389 |
Knowledge Not comparable
GPT-5.1-Codex: —, GPT-5.3 Chat: 38.8 (#140)
| Benchmark | GPT-5.1-Codex | GPT-5.3 Chat |
|---|---|---|
| LMArena Expert | — | 1397 |
Multilingual Not comparable
GPT-5.1-Codex: —, GPT-5.3 Chat: 50.3 (#124)
| Benchmark | GPT-5.1-Codex | GPT-5.3 Chat |
|---|---|---|
| LMArena Non-English | — | 1382 |
| LMArena Chinese | — | 1432 |
| LMArena French | — | 1397 |
| LMArena German | — | 1384 |
| LMArena Japanese | — | 1352 |
| LMArena Korean | — | 1346 |
| LMArena Russian | — | 1400 |
| LMArena Spanish | — | 1371 |
Instruction Following Not comparable
GPT-5.1-Codex: —, GPT-5.3 Chat: 72.8 (#129)
| Benchmark | GPT-5.1-Codex | GPT-5.3 Chat |
|---|---|---|
| LMArena Instruction Following | — | 1378 |
Long Context Not comparable
GPT-5.1-Codex: —, GPT-5.3 Chat: 42.6 (#120)
| Benchmark | GPT-5.1-Codex | GPT-5.3 Chat |
|---|---|---|
| LMArena Longer Query | — | 1396 |
Writing & Preference Not comparable
GPT-5.1-Codex: —, GPT-5.3 Chat: 63.1 (#68)
| Benchmark | GPT-5.1-Codex | GPT-5.3 Chat |
|---|---|---|
| LMArena Text | — | 1389 |
| LMArena Creative Writing | — | 1355 |
| EQ-Bench Creative Writing | — | 1690 |
| LMArena Multi-Turn | — | 1412 |
Frequently asked questions
Is GPT-5.1-Codex better than GPT-5.3 Chat?
GPT-5.3 Chat is the stronger model overall, scoring 42.8 to 38.6 on the Noometry Index.
Which is cheaper, GPT-5.1-Codex or GPT-5.3 Chat?
GPT-5.1-Codex is cheaper. It lists at $1.25 per million input tokens and $10 per million output tokens; GPT-5.3 Chat lists at $1.75 and $14.
Is GPT-5.1-Codex or GPT-5.3 Chat better for coding?
They score almost the same on coding (41.9 vs 41.4); test both on your own repository before choosing.
Which has the bigger context window?
GPT-5.1-Codex does, with 400K tokens against 128K.
How many benchmarks do GPT-5.1-Codex and GPT-5.3 Chat share?
0 benchmarks have published results for both models. GPT-5.1-Codex has 6 scored results on Noometry and GPT-5.3 Chat has 18.