GPT-5.3 Codex vs Gemini 3.1 Pro Preview vs Claude Sonnet 5
Too close to call on our weighted score (Gemini 3.1 Pro Preview 68, Claude Sonnet 5 66, GPT-5.3 Codex 64). The right pick depends on what you value most.
OpenAIGPT-5.3 Codex
64/100- ECI156.8
- Price$1.75 / $14.00
- Context400K
GoogleGemini 3.1 Pro Preview
68/100- ECI154.8
- Price$2.00 / $12.00
- Context1.05M
AnthropicClaude Sonnet 5
66/100- ECI156.3
- Price$2.00 / $10.00
- Context1M
Too close to call
It is close. Our weighted score puts them within 2 points (Gemini 3.1 Pro Preview 68/100, Claude Sonnet 5 66/100, GPT-5.3 Codex 64/100), so choose by what matters most for your work: GPT-5.3 Codex for raw capability, Claude Sonnet 5 on price and Gemini 3.1 Pro Preview for long inputs. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
- CapabilityGPT-5.3 CodexCapabilities Index (ECI): GPT-5.3 Codex 156.8 · Claude Sonnet 5 156.3 · Gemini 3.1 Pro Preview 154.8
- Lowest priceClaude Sonnet 5Claude Sonnet 5 $4.00 · Gemini 3.1 Pro Preview $4.50 · GPT-5.3 Codex $4.81 per 1M tokens (3:1 blend)
- Longest contextGemini 3.1 Pro PreviewGemini 3.1 Pro Preview 1,048,576 · Claude Sonnet 5 1,000,000 · GPT-5.3 Codex 400,000 tokens
- Widest inputsGemini 3.1 Pro PreviewGPT-5.3 Codex: Text, Images, PDFs · Gemini 3.1 Pro Preview: Text, Images, PDFs, Audio, Video · Claude Sonnet 5: Text, Images, PDFs
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | GPT-5.3 Codex | Gemini 3.1 Pro Preview | Claude Sonnet 5 |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 87 | 84 | 86 |
| Price | 25% | 18 | 19 | 21 |
| Inputs & features | 15% | 80 | 100 | 80 |
| Context window | 10% | 44 | 61 | 60 |
| Overall | 100% | 64/100 | 68/100 | 66/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | GPT-5.3 CodexOpenAI | Gemini 3.1 Pro PreviewGoogle | Claude Sonnet 5Anthropic |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 156.8 (best) | 154.8 | 156.3 |
| ECI rank | #18 of 148 (best) | #31 of 148 | #23 of 148 |
| GPQA DiamondGraduate-level science questions | — | 94.4% (best) | 90.5% |
| FrontierMath Tiers 1–3Research-level mathematics | — | 59.7% | 65.6% (best) |
| OTIS Mock AIME 2024–2025Competition mathematics | — | 95.6% (best) | 94.7% |
| SWE-bench VerifiedFixing real GitHub issues | 74.8% | 75.6% (best) | — |
| SimpleQA VerifiedShort factual questions | — | 73.5% (best) | 33.7% |
| Price per million tokens | |||
| Input | $1.75 (best) | $2.00 | $2.00 |
| Output | $14.00 | $12.00 | $10.00 (best) |
| Cached input | $0.175 (best) | $0.20 | $0.20 |
| Blended (3:1) | $4.81 | $4.50 | $4.00 (best) |
| Long-context rate | Same rate | Over 200K: $4.00 / $18.00 | Same rate |
| Price source | Official OpenAI API | Official Google API | Official Anthropic API |
| Limits | |||
| Context window | 400,000 tokens | 1,048,576 tokens (best) | 1,000,000 tokens |
| Max output | 128,000 tokens (best) | 65,536 tokens | 128,000 tokens (best) |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | Yes | Yes |
| Audio | No | Yes | No |
| Video | No | Yes | No |
| Reasoning | Yeslow · medium · high · xhigh | Yeslow · medium · high | Yeslow · medium · high · xhigh · max |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | gpt-5.3-codex | gemini-3.1-pro-preview | claude-sonnet-5 |
| API providers | 19 | 26 | 38 (best) |
| Released | Feb 5, 2026 | Feb 19, 2026 | Jun 30, 2026 |
| Knowledge cutoff | Aug 31, 2025 | Jan 2025 | Jan 31, 2026 |
What would a month cost?
Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.
- GPT-5.3 Codex$45.50
- Gemini 3.1 Pro Preview$44.00
- Claude Sonnet 5$40.00
Which should you choose?
Which is better: GPT-5.3 Codex, Gemini 3.1 Pro Preview or Claude Sonnet 5?
It is close. Our weighted score puts them within 2 points (Gemini 3.1 Pro Preview 68/100, Claude Sonnet 5 66/100, GPT-5.3 Codex 64/100), so choose by what matters most for your work: GPT-5.3 Codex for raw capability, Claude Sonnet 5 on price and Gemini 3.1 Pro Preview for long inputs. The score weighs capability 50%, price 25%, inputs & features 15%, context window 10%.
Which is cheaper, GPT-5.3 Codex, Gemini 3.1 Pro Preview or Claude Sonnet 5?
Claude Sonnet 5 is cheaper at $2.00 input / $10.00 output per million tokens (official Anthropic API price). Gemini 3.1 Pro Preview costs $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). At a typical mix of three input tokens to one output token, that is $4.00 per million tokens for Claude Sonnet 5 versus $4.50 for Gemini 3.1 Pro Preview (1.1× as much) and $4.81 for GPT-5.3 Codex (1.2× as much).
Which scores higher on benchmarks?
GPT-5.3 Codex scores higher on the Capabilities Index (ECI): GPT-5.3 Codex 156.8 (#18 of 148), Claude Sonnet 5 156.3 (#23 of 148) and Gemini 3.1 Pro Preview 154.8 (#31 of 148). The confidence ranges of the top two overlap (153.5–160.8 vs 153.6–158.8), so treat the gap as small.
Which is better for coding?
There are no published SWE-bench Verified results for Claude Sonnet 5 yet, so there is no like-for-like coding score. On overall capability, GPT-5.3 Codex 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 has the largest context window at 1,048,576 tokens, against 1,000,000 for Claude Sonnet 5 and 400,000 for GPT-5.3 Codex. Maximum output per response: GPT-5.3 Codex up to 128,000, Gemini 3.1 Pro Preview up to 65,536, Claude Sonnet 5 up to 128,000 tokens.
Which can read images, PDFs, audio or video?
GPT-5.3 Codex accepts text, images and PDFs; Gemini 3.1 Pro Preview accepts text, images, PDFs, audio and video; Claude Sonnet 5 accepts text, images and PDFs. Gemini 3.1 Pro Preview handles the widest range of inputs.
Are any of these open source?
No. GPT-5.3 Codex, Gemini 3.1 Pro Preview and Claude Sonnet 5 are proprietary and only available through APIs and apps.
Which is newer?
Claude Sonnet 5 is the newest, released Jun 30, 2026. Gemini 3.1 Pro Preview came out Feb 19, 2026; GPT-5.3 Codex came out Feb 5, 2026. Knowledge cutoff: GPT-5.3 Codex Aug 31, 2025, Gemini 3.1 Pro Preview Jan 2025, Claude Sonnet 5 Jan 31, 2026.
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.
Related comparisons
- GPT-5.3 Codex vs Kimi K3Moonshot AI · ECI 157.6
- GPT-5.3 Codex vs Qwen3.8 MaxAlibaba (Qwen) · ECI 156.6
- Gemini 3.1 Pro Preview vs Qwen3.7 MaxAlibaba (Qwen) · ECI 153.7
- Gemini 3.1 Pro Preview vs Claude Sonnet 4.6Anthropic · ECI 152.3
- Gemini 3.1 Pro Preview vs Grok 4.5xAI · ECI 154.0
- Claude Sonnet 5 vs Qwen3.8 MaxAlibaba (Qwen) · ECI 156.6
