Gemini 3.1 Pro Preview vs GPT-5.3 Codex vs GPT-5.5
Gemini 3.1 Pro Preview comes out ahead, 68 to 64 and 63 on our weighted score, and it is the cheaper option too.
- Our pick
GoogleGemini 3.1 Pro Preview
68/100- ECI154.8
- Price$2.00 / $12.00
- Context1.05M
OpenAIGPT-5.3 Codex
64/100- ECI156.8
- Price$1.75 / $14.00
- Context400K
- OpenAI
GPT-5.5
63/100- ECI159.2
- Price$5.00 / $30.00
- Context1.05M
Gemini 3.1 Pro Preview is our pick
Gemini 3.1 Pro Preview is the better all-round choice, scoring 68/100 against GPT-5.3 Codex (64) and GPT-5.5 (63). It leads on inputs & features. GPT-5.5 wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityGPT-5.5Capabilities Index (ECI): GPT-5.5 159.2 · GPT-5.3 Codex 156.8 · Gemini 3.1 Pro Preview 154.8
- Lowest priceGemini 3.1 Pro PreviewGemini 3.1 Pro Preview $4.50 · GPT-5.3 Codex $4.81 · GPT-5.5 $11.25 per 1M tokens (3:1 blend)
- Longest contextGPT-5.5 and Gemini 3.1 Pro PreviewGPT-5.5 1,050,000 · Gemini 3.1 Pro Preview 1,048,576 · GPT-5.3 Codex 400,000 tokens
- Widest inputsGemini 3.1 Pro PreviewGemini 3.1 Pro Preview: Text, Images, PDFs, Audio, Video · GPT-5.3 Codex: Text, Images, PDFs · GPT-5.5: Text, Images, PDFs
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | Gemini 3.1 Pro Preview | GPT-5.3 Codex | GPT-5.5 |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 84 | 87 | 90 |
| Price | 25% | 19 | 18 | 0 |
| Inputs & features | 15% | 100 | 80 | 80 |
| Context window | 10% | 61 | 44 | 61 |
| Overall | 100% | 68/100 | 64/100 | 63/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Gemini 3.1 Pro PreviewGoogle | GPT-5.3 CodexOpenAI | GPT-5.5OpenAI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 154.8 | 156.8 | 159.2 (best) |
| ECI rank | #31 of 148 | #18 of 148 | #10 of 148 (best) |
| GPQA DiamondGraduate-level science questions | 94.4% (best) | — | 94.0% |
| FrontierMath Tiers 1–3Research-level mathematics | 59.7% | — | 85.3% (best) |
| OTIS Mock AIME 2024–2025Competition mathematics | 95.6% | — | 100% (best) |
| SWE-bench VerifiedFixing real GitHub issues | 75.6% | 74.8% | 80.6% (best) |
| SimpleQA VerifiedShort factual questions | 73.5% (best) | — | 63.0% |
| Price per million tokens | |||
| Input | $2.00 | $1.75 (best) | $5.00 |
| Output | $12.00 (best) | $14.00 | $30.00 |
| Cached input | $0.20 | $0.175 (best) | $0.50 |
| Blended (3:1) | $4.50 (best) | $4.81 | $11.25 |
| Long-context rate | Over 200K: $4.00 / $18.00 | Same rate | Over 272K: $10.00 / $45.00 |
| Price source | Official Google API | Official OpenAI API | Official OpenAI API |
| Limits | |||
| Context window | 1,048,576 tokens | 400,000 tokens | 1,050,000 tokens (best) |
| Max output | 65,536 tokens | 128,000 tokens (best) | 128,000 tokens (best) |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | Yes | Yes |
| Audio | Yes | No | No |
| Video | Yes | No | No |
| Reasoning | Yeslow · medium · high | Yeslow · medium · high · xhigh | Yeslow · medium · high · xhigh |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | gemini-3.1-pro-preview | gpt-5.3-codex | gpt-5.5 |
| API providers | 26 | 19 | 42 (best) |
| Released | Feb 19, 2026 | Feb 5, 2026 | Apr 23, 2026 |
| Knowledge cutoff | Jan 2025 | Aug 31, 2025 | Dec 1, 2025 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- Gemini 3.1 Pro Preview$44.00
- GPT-5.3 Codex$45.50
- GPT-5.5$110.00
Which should you choose?
Which is better: Gemini 3.1 Pro Preview, GPT-5.3 Codex or GPT-5.5?
Gemini 3.1 Pro Preview is the better all-round choice, scoring 68/100 against GPT-5.3 Codex (64) and GPT-5.5 (63). It leads on inputs & features. GPT-5.5 wins on capability. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, Gemini 3.1 Pro Preview, GPT-5.3 Codex or GPT-5.5?
Gemini 3.1 Pro Preview is cheaper at $2.00 input / $12.00 output per million tokens (official Google API price). GPT-5.3 Codex costs $1.75 input / $14.00 output per million tokens (official OpenAI API price); GPT-5.5 costs $5.00 input / $30.00 output per million tokens (official OpenAI API price). At a typical mix of three input tokens to one output token, that is $4.50 per million tokens for Gemini 3.1 Pro Preview versus $4.81 for GPT-5.3 Codex (1.1× as much) and $11.25 for GPT-5.5 (2.5× as much).
Which scores higher on benchmarks?
GPT-5.5 scores higher on the Capabilities Index (ECI): GPT-5.5 159.2 (#10 of 148), GPT-5.3 Codex 156.8 (#18 of 148) and Gemini 3.1 Pro Preview 154.8 (#31 of 148). The confidence ranges of the top two overlap (156.9–162.4 vs 153.5–160.8), so treat the gap as small. On individual benchmarks: SWE-bench Verified — GPT-5.5 80.6%, Gemini 3.1 Pro Preview 75.6%, GPT-5.3 Codex 74.8%.
Which is better for coding?
GPT-5.5 resolves more real GitHub issues on SWE-bench Verified: GPT-5.5 80.6%, Gemini 3.1 Pro Preview 75.6% and GPT-5.3 Codex 74.8%. All three support tool calling for agent workflows.
Which has the bigger context window?
GPT-5.5 and Gemini 3.1 Pro Preview have the largest context windows (1,050,000 and 1,048,576 tokens), against 400,000 for GPT-5.3 Codex. Maximum output per response: Gemini 3.1 Pro Preview up to 65,536, GPT-5.3 Codex up to 128,000, GPT-5.5 up to 128,000 tokens.
Which can read images, PDFs, audio or video?
Gemini 3.1 Pro Preview accepts text, images, PDFs, audio and video; GPT-5.3 Codex accepts text, images and PDFs; GPT-5.5 accepts text, images and PDFs. Gemini 3.1 Pro Preview handles the widest range of inputs.
Are any of these open source?
No. Gemini 3.1 Pro Preview, GPT-5.3 Codex and GPT-5.5 are proprietary and only available through APIs and apps.
Which is newer?
GPT-5.5 is the newest, released Apr 23, 2026. Gemini 3.1 Pro Preview came out Feb 19, 2026; GPT-5.3 Codex came out Feb 5, 2026. Knowledge cutoff: Gemini 3.1 Pro Preview Jan 2025, GPT-5.3 Codex Aug 31, 2025, GPT-5.5 Dec 1, 2025.
How do you decide the winner?
Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Oct 4, 2026.
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