GPT-5.3-Codex vs Grok 4.3
GPT-5.3-Codex 
Grok 4.3 Verdict
- GPT-5.3-Codex leads on quality: 62.5 vs 60.7.
- GPT-5.3-Codex is stronger in agents & tools, coding, composite, long context, multimodal.
- Grok 4.3 (medium) is stronger in instruction following, knowledge.
- Grok 4.3 (medium) is 3.1× cheaper ($1.56 vs $4.81 per 1M blended).
| Metric | GPT-5.3-Codex | Grok 4.3 (medium) |
|---|---|---|
| BenchLeader Index | 62.5 | 60.7 |
| Agents & tools score | 62.7 | 60.1 |
| Coding score | 54.8 | – |
| Composite score | 70.1 | 60.3 |
| Instruction following score | 73.2 | 80.0 |
| Knowledge score | 69.3 | 72.1 |
| Long context score | 68.3 | 64.0 |
| Multimodal score | 63.0 | 60.2 |
| Blended price $/M | $4.81 | $1.56 |
| Output speed | 121 tok/s | 112 tok/s |
| Time to first answer | 58.2 s | 12.1 s |
| Context window | 400k | 1M |
| Terminal-Bench | 78.4% | – |
| WeirdML | 79.3% | – |
| APEX-Agents | 31.8% | – |
| Epoch Capabilities Index | 156.6 | – |
| LMArena WebDev | 1409 | – |
| AA Intelligence Index | 32.5 | 24.8 |
| IFBench | 75.4% | 83.3% |
| AA-LCR | 83.3% | 75.0% |
| MMMU-Pro | 78.5% | 75.8% |
| AA-Omniscience | 10.9 | 16.7 |
| Terminal-Bench Hard | 53.0% | 30.3% |
| GPQA Diamond (AA) | 91.5% | 89.0% |
| Humanity's Last Exam (AA) | 42.5% | 30.0% |
| τ²-Bench Telecom (AA) | 86.0% | 91.2% |
| HiL-Bench | 4.3% | – |
Data as of 2026-09-10. Best configuration of each model; every score links to its source on the model pages.
GPT-5.3-Codex vs Grok 4.3: questions
- Is GPT-5.3-Codex better than Grok 4.3?
- GPT-5.3-Codex leads on quality: 62.5 vs 60.7. The BenchLeader Index combines every independent quality benchmark; GPT-5.3-Codex is ahead overall as of 2026-09-10, but check the category scores for your use.
- Is GPT-5.3-Codex better than Grok 4.3 for agentic tasks?
- GPT-5.3-Codex scores higher in agentic tasks (63 vs 60 on the category index, where 50 is average).
- Which is cheaper, GPT-5.3-Codex or Grok 4.3?
- Grok 4.3 is cheaper: $1.56 against $4.81 per million tokens, blended at three input tokens per output token.
- Which is faster, GPT-5.3-Codex or Grok 4.3?
- GPT-5.3-Codex streams faster: 121 against 112 output tokens per second.
- Which has the larger context window?
- Grok 4.3 accepts more context: 1M against 400k tokens.