Model comparison
GLM-5.3-Flash vs GPT-5.5 Pro
GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 51.8 on the Noometry Index. GLM-5.3-Flash costs 284× less per token, which makes it the better buy when GPT-5.5 Pro's lead doesn't matter for your workload.
Last verified . 9 shared benchmarks.
Summary
- They share 9 benchmarks with published results for both. GLM-5.3-Flash scores higher in 0 categories and GPT-5.5 Pro in 3 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in math, where GPT-5.5 Pro leads 84.0 to 53.3.
- The biggest single-benchmark swing is FrontierMath Tier 4: 17.1% for GLM-5.3-Flash and 78% for GPT-5.5 Pro.
- GLM-5.3-Flash is cheaper at $0.15 / $0.50 per million input/output tokens, against $30 / $180 for GPT-5.5 Pro.
- GPT-5.5 Pro accepts more context: 1.05M tokens versus 1M.
- GLM-5.3-Flash has downloadable open weights; the other is API-only.
Side by side
| GLM-5.3-Flash | GPT-5.5 Pro | |
|---|---|---|
| Provider | Z.ai (Zhipu) | OpenAI |
| Noometry Index | 51.8 | 64.3 |
| Released | 2026-08-20 | 2026-04-23 |
| Weights | Open | Proprietary |
| Context window | 1M | 1.05M |
| Max output | 131K | 128K |
| Input $ / M tokens | $0.15 | $30 |
| Output $ / M tokens | $0.50 | $180 |
| Results tracked | 40 | 14 |
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Category by category
Coding Not comparable
GLM-5.3-Flash: 53.1 (#31), GPT-5.5 Pro: —
| Benchmark | GLM-5.3-Flash | GPT-5.5 Pro |
|---|---|---|
| DeepSWE | 63.4% | — |
| FrontierCode | 31.8% | — |
| CursorBench | 36.8% | — |
| LMArena WebDev | 1609 | — |
| FrontierSWE | 18.1% | — |
| SciCode | 51.6% | — |
| LMArena Coding | 1508 | — |
| ALE-Bench | 303.55 | — |
Agentic & Tool Use Not comparable
GLM-5.3-Flash: 34.2 (#47), GPT-5.5 Pro: —
| Benchmark | GLM-5.3-Flash | GPT-5.5 Pro |
|---|---|---|
| APEX-Agents | 52.8% | — |
| GDP.pdf | 14% | — |
Reasoning GPT-5.5 Pro leads
GLM-5.3-Flash: 48.0 (#42), GPT-5.5 Pro: 73.3 (#10)
| Benchmark | GLM-5.3-Flash | GPT-5.5 Pro |
|---|---|---|
| ARC-AGI-2 | 65.8% | 84.6% |
| ARC-AGI-1 | 91% | 96.5% |
| CritPt | 15.4% | 30.6% |
| Chess Puzzles | 14% | 64% |
| Epoch Capabilities Index | 151.88 | 162.07 |
| SimpleBench | — | 76.9% |
| LMArena Hard Prompts | 1491 | — |
| Mystery Game Puzzles | 8% | — |
| DTBench | — | 96% |
| LMCA | — | 53.9% |
| Surface Evolver Bench | 52.5% | — |
| Bench to the Future 3 | 0.15 | — |
Math GPT-5.5 Pro leads
GLM-5.3-Flash: 53.3 (#47), GPT-5.5 Pro: 84.0 (#10)
| Benchmark | GLM-5.3-Flash | GPT-5.5 Pro |
|---|---|---|
| FrontierMath (Tiers 1-3) | 55.8% | 87.7% |
| FrontierMath Tier 4 | 17.1% | 78% |
| OTIS Mock AIME 2024-2025 | 93.9% | 100% |
| ProofBench | 21% | — |
| LMArena Math | 1500 | — |
| FrontierMath (Feb 2025 set) | — | 52.4% |
| FrontierMath Tier 4 (v1) | — | 39.6% |
Knowledge GPT-5.5 Pro leads
GLM-5.3-Flash: 58.4 (#36), GPT-5.5 Pro: 64.1 (#19)
| Benchmark | GLM-5.3-Flash | GPT-5.5 Pro |
|---|---|---|
| GPQA Diamond | 90.2% | 93.9% |
| LMArena Expert | 1513 | — |
Multimodal Not comparable
GLM-5.3-Flash: 42.8 (#27), GPT-5.5 Pro: —
| Benchmark | GLM-5.3-Flash | GPT-5.5 Pro |
|---|---|---|
| LMArena Vision | 1296 | — |
Multilingual Not comparable
GLM-5.3-Flash: 56.0 (#25), GPT-5.5 Pro: —
| Benchmark | GLM-5.3-Flash | GPT-5.5 Pro |
|---|---|---|
| LMArena Non-English | 1462 | — |
| LMArena Chinese | 1527 | — |
| LMArena French | 1496 | — |
| LMArena German | 1470 | — |
| LMArena Japanese | 1429 | — |
| LMArena Korean | 1446 | — |
| LMArena Russian | 1469 | — |
| LMArena Spanish | 1471 | — |
Instruction Following Not comparable
GLM-5.3-Flash: 77.5 (#20), GPT-5.5 Pro: —
| Benchmark | GLM-5.3-Flash | GPT-5.5 Pro |
|---|---|---|
| LMArena Instruction Following | 1478 | — |
Long Context Not comparable
GLM-5.3-Flash: 45.4 (#39), GPT-5.5 Pro: —
| Benchmark | GLM-5.3-Flash | GPT-5.5 Pro |
|---|---|---|
| LMArena Longer Query | 1482 | — |
Writing & Preference Not comparable
GLM-5.3-Flash: 65.3 (#50), GPT-5.5 Pro: —
| Benchmark | GLM-5.3-Flash | GPT-5.5 Pro |
|---|---|---|
| LMArena Text | 1471 | — |
| LMArena Creative Writing | 1442 | — |
| LMArena Multi-Turn | 1467 | — |
Frequently asked questions
Is GLM-5.3-Flash better than GPT-5.5 Pro?
GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 51.8 on the Noometry Index. GLM-5.3-Flash costs 284× less per token, which makes it the better buy when GPT-5.5 Pro's lead doesn't matter for your workload.
Which is cheaper, GLM-5.3-Flash or GPT-5.5 Pro?
GLM-5.3-Flash is cheaper. It lists at $0.15 per million input tokens and $0.50 per million output tokens; GPT-5.5 Pro lists at $30 and $180.
Which has the bigger context window?
GPT-5.5 Pro does, with 1.05M tokens against 1M.
How many benchmarks do GLM-5.3-Flash and GPT-5.5 Pro share?
9 benchmarks have published results for both models. GLM-5.3-Flash has 40 scored results on Noometry and GPT-5.5 Pro has 14.