GPT-5.1-Codex is a specialized version of GPT-5.1 optimized for software engineering and coding workflows. It is designed for both interactive development sessions and long, independent execution of complex engineering tasks. The model supp…
Model details →OpenAI: GPT-5.1-Codex vs OpenAI: o1
OpenAI: GPT-5.1-Codex wins on 3 of 6 axes — pricing and capability skew in its favour for most workloads.
The latest and strongest model family from OpenAI, o1 is designed to spend more time thinking before responding. The o1 model series is trained with large-scale reinforcement learning to reason using chain of thought. The o1 models are op…
Model details →Side-by-side comparison
| Capability | OpenAI: GPT-5.1-Codex | OpenAI: o1 | Winner |
|---|---|---|---|
| Context window Maximum number of input tokens the model can attend to in a single request. | 400K | 200K | 🏆 OpenAI: GPT-5.1-Codex |
| Input price (per 1M) Cost per million input tokens billed by the provider. | $1.25 | $15.00 | 🏆 OpenAI: GPT-5.1-Codex |
| Output price (per 1M) Cost per million output tokens billed by the provider. | $10.00 | $60.00 | 🏆 OpenAI: GPT-5.1-Codex |
| Tool / function calling First-class support for emitting structured tool calls. | Yes | Yes | Tie |
| Vision input Accepts image inputs alongside text. | Yes | Yes | Tie |
| Reasoning mode Internal chain-of-thought / extended-thinking support. | Yes | Yes | Tie |
Frequently asked questions
Is OpenAI: GPT-5.1-Codex better than OpenAI: o1?
OpenAI: GPT-5.1-Codex wins on 3 of 6 axes — pricing and capability skew in its favour for most workloads.
What's the price difference between OpenAI: GPT-5.1-Codex and OpenAI: o1?
Input: $1.25 vs $15.00 per 1M tokens. Output: $10.00 vs $60.00 per 1M tokens.
What context windows do OpenAI: GPT-5.1-Codex and OpenAI: o1 support?
OpenAI: GPT-5.1-Codex supports up to 400K tokens. OpenAI: o1 supports up to 200K tokens.
Do both OpenAI: GPT-5.1-Codex and OpenAI: o1 support tool calling?
OpenAI: GPT-5.1-Codex: yes. OpenAI: o1: yes.