Model comparison
GPT-5.3 Chat vs Step 3.5 Flash
GPT-5.3 Chat and Step 3.5 Flash score almost the same on the Noometry Index (42.8 vs 42.3), so choose on price, context window or the category you care about most.
Last verified . 17 shared benchmarks.
StepFunSummary
- They share 17 benchmarks with published results for both. GPT-5.3 Chat scores higher in 2 categories and Step 3.5 Flash in 6 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where GPT-5.3 Chat leads 28.5 to 22.2.
- Step 3.5 Flash is cheaper at $0.10 / $0.30 per million input/output tokens, against $1.75 / $14 for GPT-5.3 Chat.
- Step 3.5 Flash accepts more context: 256K tokens versus 128K.
- Step 3.5 Flash has downloadable open weights; the other is API-only.
Side by side
| GPT-5.3 Chat | Step 3.5 Flash | |
|---|---|---|
| Provider | OpenAI | StepFun |
| Noometry Index | 42.8 | 42.3 |
| Released | 2026-03-03 | 2026-01-29 |
| Weights | Proprietary | Open |
| Context window | 128K | 256K |
| Max output | 16K | 256K |
| Input $ / M tokens | $1.75 | $0.10 |
| Output $ / M tokens | $14 | $0.30 |
| Results tracked | 18 | 19 |
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Category by category
Coding Too close to call
GPT-5.3 Chat: 41.4 (#124), Step 3.5 Flash: 42.4 (#105)
| Benchmark | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| LMArena Coding | 1408 | 1436 |
Reasoning GPT-5.3 Chat leads
GPT-5.3 Chat: 28.5 (#102), Step 3.5 Flash: 22.2 (#202)
| Benchmark | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| LMArena Hard Prompts | 1399 | 1411 |
| NYT Connections (extended) | — | 28.4% |
Math Step 3.5 Flash leads
GPT-5.3 Chat: 38.2 (#142), Step 3.5 Flash: 42.6 (#84)
| Benchmark | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| LMArena Math | 1389 | 1408 |
| MathArena Final-Answer Competitions | — | 66.8% |
Knowledge Too close to call
GPT-5.3 Chat: 38.8 (#140), Step 3.5 Flash: 39.6 (#132)
| Benchmark | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| LMArena Expert | 1397 | 1421 |
Multilingual Too close to call
GPT-5.3 Chat: 50.3 (#124), Step 3.5 Flash: 50.5 (#119)
| Benchmark | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| LMArena Non-English | 1382 | 1385 |
| LMArena Chinese | 1432 | 1447 |
| LMArena French | 1397 | 1421 |
| LMArena German | 1384 | 1405 |
| LMArena Japanese | 1352 | 1354 |
| LMArena Korean | 1346 | 1352 |
| LMArena Russian | 1400 | 1385 |
| LMArena Spanish | 1371 | 1419 |
Instruction Following Too close to call
GPT-5.3 Chat: 72.8 (#129), Step 3.5 Flash: 73.1 (#124)
| Benchmark | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| LMArena Instruction Following | 1378 | 1385 |
Long Context Too close to call
GPT-5.3 Chat: 42.6 (#120), Step 3.5 Flash: 42.8 (#117)
| Benchmark | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| LMArena Longer Query | 1396 | 1402 |
Writing & Preference GPT-5.3 Chat leads
GPT-5.3 Chat: 63.1 (#68), Step 3.5 Flash: 58.8 (#113)
| Benchmark | GPT-5.3 Chat | Step 3.5 Flash |
|---|---|---|
| LMArena Text | 1389 | 1403 |
| LMArena Creative Writing | 1355 | 1357 |
| LMArena Multi-Turn | 1412 | 1405 |
| EQ-Bench Creative Writing | 1690 | — |
Frequently asked questions
Is GPT-5.3 Chat better than Step 3.5 Flash?
GPT-5.3 Chat and Step 3.5 Flash score almost the same on the Noometry Index (42.8 vs 42.3), so choose on price, context window or the category you care about most.
Which is cheaper, GPT-5.3 Chat or Step 3.5 Flash?
Step 3.5 Flash is cheaper. It lists at $0.10 per million input tokens and $0.30 per million output tokens; GPT-5.3 Chat lists at $1.75 and $14.
Is GPT-5.3 Chat or Step 3.5 Flash better for coding?
They score almost the same on coding (41.4 vs 42.4); test both on your own repository before choosing.
Which has the bigger context window?
Step 3.5 Flash does, with 256K tokens against 128K.
How many benchmarks do GPT-5.3 Chat and Step 3.5 Flash share?
17 benchmarks have published results for both models. GPT-5.3 Chat has 18 scored results on Noometry and Step 3.5 Flash has 19.