AI model comparison
GPT-5.1-Codex vs o3
Pricing, context window, benchmarks, and features compared side by side. Or skip the guesswork and send one prompt to both.
OpenAI
GPT-5.1-Codex
GPT-5.1-Codex is a specialized version of GPT-5.1 optimized for software engineering and coding workflows.
- Input / 1M
- $1.25
- Output / 1M
- $10
- Context
- 400K
OpenAI
o3
o3 is a well-rounded and powerful model across domains. It sets a new standard for math, science, coding, and visual reasoning tasks.
- Input / 1M
- $2
- Output / 1M
- $8
- Context
- 200K
At a glance
Quick verdict
How the two models stack up on the things people ask about most.
Lower price
GPT-5.1-Codex
1.1x cheaper for a typical chat
Higher intelligence score
GPT-5.1-Codex
23.7 vs 20.2 on Artificial Analysis
Larger context window
GPT-5.1-Codex
400K vs 200K tokens
Newer release
GPT-5.1-Codex
Released November 13, 2025
Benchmarks
Benchmark scores
Independent scores from Artificial Analysis. Higher is better.
Intelligence index
GPT-5.1-Codex23.7o320.2Coding index
GPT-5.1-CodexNot availableo3Not availableAgentic index
GPT-5.1-CodexNot availableo3Not availablePricing
GPT-5.1-Codex vs o3 API pricing
Per-token API rates. Cheaper option highlighted.
| Metric | GPT-5.1-Codex | o3 |
|---|---|---|
| Input tokensPer 1M tokens | $1.25 | $2 |
| Output tokensPer 1M tokens | $10 | $8 |
| Cached input (read)Per 1M tokens | $0.13 | $0.50 |
| Cache writePer 1M tokens | Not available | Not available |
| Web searchPer request | $0.01 | $0.01 |
What it costs in practice
Estimated cost per 1,000 requests at standard rates. Coding and long-document figures also show the cost when the input is already cached.
Chat message
2K in, 500 out
GPT-5.1-Codex$7.50o3$8Coding task
30K in, 4K out
GPT-5.1-Codex$77.50$43.90 cachedo3$92$47 cachedLong document summary
150K in, 2K out
GPT-5.1-Codex$207.50$39.50 cachedo3$316$91 cachedSpecs
Context window and capabilities
How much each model can read, how much it can write, and what it accepts as input.
| Metric | GPT-5.1-Codex | o3 |
|---|---|---|
| Context window | 400K tokens | 200K tokens |
| Max output | 128K tokens | 100K tokens |
| Input types | Image, Text | File, Image, Text |
| Output types | Text | Text |
| Reasoning effort levels | High, Medium, Low | Not available |
| Default reasoning effort | Medium | Not available |
| Release date | November 13, 2025 | April 16, 2025 |
Features
Supported features
API features available for each model.
| Metric | GPT-5.1-Codex | o3 |
|---|---|---|
| Tool calling | Supported | Supported |
| Structured outputs | Supported | Supported |
| JSON mode | Supported | Supported |
| Reasoning | Supported | Supported |
| Temperature | Not supported | Not supported |
| Stop sequences | Not supported | Not supported |
| Deterministic seed | Supported | Supported |
| Verbosity control | Supported | Not supported |
Keep exploring
More on these models
Other head-to-heads, the full model page, and the alternatives list for each model.
GPT-5.1-CodexView full model details- GPT-5.1-Codex vs GPT-5.2
- GPT-5.1-Codex vs GPT-5.2-Codex
- GPT-5.1-Codex vs Gemini 3 Flash Preview
- GPT-5.1-Codex vs GPT-5.1
- GPT-5.1-Codex vs DeepSeek V4 Flash 0423
- GPT-5.1-Codex vs GPT-5.4 Mini
- GPT-5.1-Codex vs GPT-5
- GPT-5.1-Codex vs Claude Opus 4.1
- GPT-5.1-Codex vs o3 Pro
- GPT-5.1-Codex vs Claude Sonnet 4.5
- GPT-5.1-Codex vs GPT-5 Mini
- GPT-5.1-Codex vs Claude Sonnet 4
Our take
GPT-5.1-Codex is 1.1x cheaper for a typical chat. GPT-5.1-Codex scores higher on the Artificial Analysis Intelligence Index (23.7 vs 20.2). GPT-5.1-Codex has the larger context window (400K vs 200K tokens). The right pick depends on your workload, so the quickest way to settle it is to send the same prompt to both and compare.
FAQ
Frequently asked questions
Is GPT-5.1-Codex or o3 cheaper?
GPT-5.1-Codex is cheaper for a typical chat (2K input tokens and 500 output tokens). GPT-5.1-Codex costs $1.25 per 1M input tokens and $10 per 1M output tokens, while o3 costs $2 per 1M input tokens and $8 per 1M output tokens.
Which has a bigger context window, GPT-5.1-Codex or o3?
GPT-5.1-Codex supports up to 400K tokens of context, compared with 200K for o3.
Is GPT-5.1-Codex smarter than o3?
On the Artificial Analysis Intelligence Index, GPT-5.1-Codex scores 23.7 and o3 scores 20.2, putting GPT-5.1-Codex ahead. Benchmarks don't capture everything, so the best test is running your own prompts through both.
Can I use GPT-5.1-Codex and o3 at the same time?
Yes. Shortcut Chat sends one prompt to multiple models at once, so you can see GPT-5.1-Codex and o3 answer side by side and keep the better response.
Why choose? Ask both.
Send one prompt to GPT-5.1-Codex and o3 at the same time. Compare the answers side by side and keep the best one.