Gemini 3.1 Pro Preview vs Kimi K3 vs GPT-5.3 Codex
Too close to call on our weighted score (Gemini 3.1 Pro Preview 68, Kimi K3 65, GPT-5.3 Codex 64). The right pick depends on what you value most.
GoogleGemini 3.1 Pro Preview
68/100- ECI154.8
- Price$2.00 / $12.00
- Context1.05M
Moonshot AIKimi K3
65/100- ECI157.6
- Price$3.00 / $15.00
- Context1.05M
OpenAIGPT-5.3 Codex
64/100- ECI156.8
- Price$1.75 / $14.00
- Context400K
Too close to call
It is close. Our weighted score puts them within 3 points (Gemini 3.1 Pro Preview 68/100, Kimi K3 65/100, GPT-5.3 Codex 64/100), so choose by what matters most for your work: Kimi K3 for raw capability and Gemini 3.1 Pro Preview on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityKimi K3Capabilities Index (ECI): Kimi K3 157.6 · 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 · Kimi K3 $6.00 per 1M tokens (3:1 blend)
- Longest contextGemini 3.1 Pro Preview and Kimi K3Gemini 3.1 Pro Preview 1,048,576 · Kimi K3 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 · Kimi K3: Text, Images, Video · GPT-5.3 Codex: Text, Images, PDFs
- Self-hostingKimi K3Publishes downloadable weights
| Measure | Weight | Gemini 3.1 Pro Preview | Kimi K3 | GPT-5.3 Codex |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 84 | 88 | 87 |
| Price | 25% | 19 | 13 | 18 |
| Inputs & features | 15% | 100 | 80 | 80 |
| Context window | 10% | 61 | 61 | 44 |
| Overall | 100% | 68/100 | 65/100 | 64/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | Gemini 3.1 Pro PreviewGoogle | Kimi K3Moonshot AI | GPT-5.3 CodexOpenAI |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 154.8 | 157.6 (best) | 156.8 |
| ECI rank | #31 of 148 | #13 of 148 (best) | #18 of 148 |
| GPQA DiamondGraduate-level science questions | 94.4% (best) | 93.1% | — |
| FrontierMath Tiers 1–3Research-level mathematics | 59.7% | 72.2% (best) | — |
| OTIS Mock AIME 2024–2025Competition mathematics | 95.6% | 97.2% (best) | — |
| SWE-bench VerifiedFixing real GitHub issues | 75.6% (best) | — | 74.8% |
| SimpleQA VerifiedShort factual questions | 73.5% (best) | 50.6% | — |
| Price per million tokens | |||
| Input | $2.00 | $3.00 | $1.75 (best) |
| Output | $12.00 (best) | $15.00 | $14.00 |
| Cached input | $0.20 | $0.30 | $0.175 (best) |
| Blended (3:1) | $4.50 (best) | $6.00 | $4.81 |
| Long-context rate | Over 200K: $4.00 / $18.00 | Same rate | Same rate |
| Price source | Official Google API | Official Moonshot AI API | Official OpenAI API |
| Limits | |||
| Context window | 1,048,576 tokens (best) | 1,048,576 tokens (best) | 400,000 tokens |
| Max output | 65,536 tokens | 131,072 tokens (best) | 128,000 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | No | Yes |
| Audio | Yes | No | No |
| Video | Yes | Yes | No |
| Reasoning | Yeslow · medium · high | Yeslow · high · max | Yeslow · medium · high · xhigh |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Open | Proprietary |
| API model ID | gemini-3.1-pro-preview | kimi-k3 | gpt-5.3-codex |
| API providers | 26 | 68 (best) | 19 |
| Released | Feb 19, 2026 | Jul 16, 2026 | Feb 5, 2026 |
| Knowledge cutoff | Jan 2025 | — | Aug 31, 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
- Kimi K3$60.00
- GPT-5.3 Codex$45.50
Which should you choose?
Which is better: Gemini 3.1 Pro Preview, Kimi K3 or GPT-5.3 Codex?
It is close. Our weighted score puts them within 3 points (Gemini 3.1 Pro Preview 68/100, Kimi K3 65/100, GPT-5.3 Codex 64/100), so choose by what matters most for your work: Kimi K3 for raw capability and Gemini 3.1 Pro Preview on price. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, Gemini 3.1 Pro Preview, Kimi K3 or GPT-5.3 Codex?
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); Kimi K3 costs $3.00 input / $15.00 output per million tokens (official Moonshot AI 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 $6.00 for Kimi K3 (1.3× as much).
Which scores higher on benchmarks?
Kimi K3 scores higher on the Capabilities Index (ECI): Kimi K3 157.6 (#13 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 (154.9–160.4 vs 153.5–160.8), so treat the gap as small.
Which is better for coding?
There are no published SWE-bench Verified results for Kimi K3 yet, so there is no like-for-like coding score. On overall capability, Kimi K3 leads, which tends to carry over to coding, but test on your own codebase. All three support tool calling for agent workflows.
Which has the bigger context window?
Gemini 3.1 Pro Preview and Kimi K3 have the largest context windows (1,048,576 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, Kimi K3 up to 131,072, GPT-5.3 Codex 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; Kimi K3 accepts text, images and video; GPT-5.3 Codex accepts text, images and PDFs. Gemini 3.1 Pro Preview handles the widest range of inputs.
Are any of these open source?
Kimi K3 publishes its weights and can be self-hosted; Gemini 3.1 Pro Preview and GPT-5.3 Codex is proprietary.
Which is newer?
Kimi K3 is the newest, released Jul 16, 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.
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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