GPT-5.1 vs GPT-5.3 Codex
Head-to-head specifications
| Metric | GPT-5.1 | GPT-5.3 Codex | Difference |
|---|---|---|---|
| Intelligence Index | 37.0 | 44.0 | -15.9% |
| Context window | 512K tokens | 922K tokens | — |
| Blended price ($/1M tokens) | $0.77 | $1.05 | -26.7% |
| Output speed (tokens/s) | 106 | 85 | +24.7% |
| Access | Proprietary API | Proprietary API | — |
- GPT-5.3 Codex leads overall capability (Intelligence Index 44.0 vs 37.0).
- GPT-5.1 is the cheaper model to run at $0.77/1M blended tokens — about 1.4× cheaper.
- GPT-5.3 Codex offers the larger context window (922K tokens), useful for long documents and codebases.
Verdict: GPT-5.1 or GPT-5.3 Codex?
GPT-5.1 advantages
- Affordability (+27%)
- Output speed (+20%)
GPT-5.3 Codex advantages
- General intelligence (+16%)
- Context window (+44%)
Which should you choose?
- Choose the GPT-5.1 if you want the lowest cost per token at scale.
- Choose the GPT-5.3 Codex if you need the strongest overall reasoning and accuracy.
- Choose the GPT-5.1 if low latency and fast generation matter for your application.
Value for money
GPT-5.1 offers more intelligence per dollar (1.1× the Intelligence-Index-per-cost of the alternative), making it the stronger value for high-volume use.
GPT-5.1 vs GPT-5.3 Codex: which should you choose?
GPT-5.1 — OpenAI multimodal model with an Intelligence Index of 37, a 512K-token context window and a blended price of $0.77/1M tokens.
GPT-5.3 Codex — OpenAI multimodal model with an Intelligence Index of 44, a 922K-token context window and a blended price of $1.05/1M tokens.
GPT-5.1 vs GPT-5.3 Codex: GPT-5.3 Codex scores higher on the Intelligence Index. GPT-5.3 Codex leads overall capability (Intelligence Index 44.0 vs 37.0). GPT-5.1 is the cheaper model to run at $0.77/1M blended tokens — about 1.4× cheaper.
Capability: intelligence, coding and agentic work
On the composite Intelligence Index the GPT-5.3 Codex scores 44.0 versus 37.0. Composite indices summarize many evaluations, but always test on your own workload before committing.
Context window and speed
The GPT-5.3 Codex accepts up to 922K tokens per request, which sets how much documentation, transcript or code it can reason over at once. In measured throughput, GPT-5.1 generates faster (106 vs 85 tokens/s), which matters for interactive apps and high-volume pipelines.
Pricing and access
At blended per-token rates, GPT-5.1 is the cheaper model to run ($0.77 vs $1.05 per 1M tokens). GPT-5.1 is proprietary api and GPT-5.3 Codex is proprietary api. Open-weight models can be self-hosted, trading per-call cost for infrastructure you manage; for production also weigh rate limits, throughput and data-residency requirements.
The verdict
Both are credible choices in the ai model comparison space; the specification table above lays out every metric so you can weigh the trade-offs that matter to you. Pick the one whose strengths line up with how you will actually use it.
Frequently asked questions
Is the GPT-5.1 better than the GPT-5.3 Codex?
These two are closely matched — the right pick comes down to which specific strengths you value and the price you actually pay. GPT-5.3 Codex leads overall capability (Intelligence Index 44.0 vs 37.0).
What is the main difference between the GPT-5.1 and the GPT-5.3 Codex?
GPT-5.3 Codex leads overall capability (Intelligence Index 44.0 vs 37.0). GPT-5.1 is the cheaper model to run at $0.77/1M blended tokens — about 1.4× cheaper.
Which is better value?
GPT-5.1 offers more intelligence per dollar (1.1× the Intelligence-Index-per-cost of the alternative), making it the stronger value for high-volume use.
Which should I choose?
Choose the GPT-5.1 if you want the lowest cost per token at scale. Choose the GPT-5.3 Codex if you need the strongest overall reasoning and accuracy.
Methodology
Large language models are compared on independent leaderboard metrics: an Intelligence Index (a composite of reasoning and knowledge evaluations), Coding and Agentic indices where measured, community arena Elo, maximum context window, a blended API price per million tokens (weighted across cache-hit, input and output rates), and measured output speed in tokens per second. Where a model ships multiple reasoning-effort variants, we report its strongest variant. Benchmarks capture only part of real-world quality, which also depends on tool use, latency, safety and task fit — and this space moves quickly, so figures reflect the leaderboard snapshot on the page date.