Model comparison
GPT-5.5 Instant vs GPT-5-Codex
GPT-5.5 Instant is the stronger model overall, scoring 42.7 to 37.9 on the Noometry Index.
Last verified . 0 shared benchmarks.
Summary
- The widest gap is in reasoning, where GPT-5-Codex leads 30.9 to 24.9.
Side by side
| GPT-5.5 Instant | GPT-5-Codex | |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Noometry Index | 42.7 | 37.9 |
| Released | 2026-05-05 | 2025-09-15 |
| Weights | Proprietary | Proprietary |
| Context window | — | 400K |
| Max output | — | 128K |
| Input $ / M tokens | — | $1.25 |
| Output $ / M tokens | — | $10 |
| Results tracked | 27 | 3 |
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Category by category
Coding GPT-5.5 Instant leads
GPT-5.5 Instant: 44.3 (#74), GPT-5-Codex: 42.4 (#103)
| Benchmark | GPT-5.5 Instant | GPT-5-Codex |
|---|---|---|
| SciCode | 48.6% | — |
| WeirdML | — | 54.5% |
| LMArena Coding | 1433 | — |
Agentic & Tool Use Not comparable
GPT-5.5 Instant: —, GPT-5-Codex: 31.0 (#72)
| Benchmark | GPT-5.5 Instant | GPT-5-Codex |
|---|---|---|
| Terminal-Bench | — | 44.3% |
Reasoning GPT-5-Codex leads
GPT-5.5 Instant: 24.9 (#155), GPT-5-Codex: 30.9 (#83)
| Benchmark | GPT-5.5 Instant | GPT-5-Codex |
|---|---|---|
| Kagi LLM Benchmark | — | 70.3% |
| CritPt | 0% | — |
| Chess Puzzles | 12% | — |
| LMArena Hard Prompts | 1426 | — |
| Epoch Capabilities Index | 142.52 | — |
Math Not comparable
GPT-5.5 Instant: 26.5 (#259), GPT-5-Codex: —
| Benchmark | GPT-5.5 Instant | GPT-5-Codex |
|---|---|---|
| FrontierMath (Tiers 1-3) | 26.3% | — |
| FrontierMath Tier 4 | 2.4% | — |
| OTIS Mock AIME 2024-2025 | 68.1% | — |
| LMArena Math | 1420 | — |
Knowledge Not comparable
GPT-5.5 Instant: 48.9 (#74), GPT-5-Codex: —
| Benchmark | GPT-5.5 Instant | GPT-5-Codex |
|---|---|---|
| GPQA Diamond | 82.5% | — |
| LMArena Expert | 1409 | — |
Multimodal Not comparable
GPT-5.5 Instant: 40.0 (#52), GPT-5-Codex: —
| Benchmark | GPT-5.5 Instant | GPT-5-Codex |
|---|---|---|
| LMArena Vision | 1250 | — |
| LMArena Document | 1403 | — |
Multilingual Not comparable
GPT-5.5 Instant: 52.8 (#80), GPT-5-Codex: —
| Benchmark | GPT-5.5 Instant | GPT-5-Codex |
|---|---|---|
| LMArena Non-English | 1417 | — |
| LMArena Chinese | 1456 | — |
| LMArena French | 1428 | — |
| LMArena German | 1411 | — |
| LMArena Japanese | 1408 | — |
| LMArena Korean | 1392 | — |
| LMArena Russian | 1431 | — |
| LMArena Spanish | 1429 | — |
Instruction Following Not comparable
GPT-5.5 Instant: 74.2 (#100), GPT-5-Codex: —
| Benchmark | GPT-5.5 Instant | GPT-5-Codex |
|---|---|---|
| LMArena Instruction Following | 1406 | — |
Long Context Not comparable
GPT-5.5 Instant: 43.4 (#96), GPT-5-Codex: —
| Benchmark | GPT-5.5 Instant | GPT-5-Codex |
|---|---|---|
| LMArena Longer Query | 1422 | — |
Writing & Preference Not comparable
GPT-5.5 Instant: 61.8 (#85), GPT-5-Codex: —
| Benchmark | GPT-5.5 Instant | GPT-5-Codex |
|---|---|---|
| LMArena Text | 1419 | — |
| LMArena Creative Writing | 1419 | — |
| LMArena Multi-Turn | 1433 | — |
Frequently asked questions
Is GPT-5.5 Instant better than GPT-5-Codex?
GPT-5.5 Instant is the stronger model overall, scoring 42.7 to 37.9 on the Noometry Index.
Is GPT-5.5 Instant or GPT-5-Codex better for coding?
GPT-5.5 Instant scores higher on coding benchmarks: 44.3 versus 42.4 in the Noometry coding category.
How many benchmarks do GPT-5.5 Instant and GPT-5-Codex share?
0 benchmarks have published results for both models. GPT-5.5 Instant has 27 scored results on Noometry and GPT-5-Codex has 3.