GPT-5.3 Codex vs Claude Sonnet 5 vs Gemini 3.1 Pro Preview
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
AnthropicClaude Sonnet 5
66/100- ECI156.3
- Price$2.00 / $10.00
- Context1M
GoogleGemini 3.1 Pro Preview
68/100- ECI154.8
- Price$2.00 / $12.00
- Context1.05M
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 · Claude Sonnet 5: Text, Images, PDFs · Gemini 3.1 Pro Preview: Text, Images, PDFs, Audio, Video
- Self-hostingNo open weightsAll three are available only through APIs
| Measure | Weight | GPT-5.3 Codex | Claude Sonnet 5 | Gemini 3.1 Pro Preview |
|---|---|---|---|---|
| CapabilityCapabilities Index (ECI) | 50% | 87 | 86 | 84 |
| Price | 25% | 18 | 21 | 19 |
| Inputs & features | 15% | 80 | 80 | 100 |
| Context window | 10% | 44 | 60 | 61 |
| Overall | 100% | 64/100 | 66/100 | 68/100 |
Every spec in one table
Highlighted cells lead their row. Dashes mean the data is not published.
| Specification | GPT-5.3 CodexOpenAI | Claude Sonnet 5Anthropic | Gemini 3.1 Pro PreviewGoogle |
|---|---|---|---|
| Capability | |||
| Capabilities Index (ECI) | 156.8 (best) | 156.3 | 154.8 |
| ECI rank | #18 of 148 (best) | #23 of 148 | #31 of 148 |
| GPQA DiamondGraduate-level science questions | — | 90.5% | 94.4% (best) |
| FrontierMath Tiers 1–3Research-level mathematics | — | 65.6% (best) | 59.7% |
| OTIS Mock AIME 2024–2025Competition mathematics | — | 94.7% | 95.6% (best) |
| SWE-bench VerifiedFixing real GitHub issues | 74.8% | — | 75.6% (best) |
| SimpleQA VerifiedShort factual questions | — | 33.7% | 73.5% (best) |
| Price per million tokens | |||
| Input | $1.75 (best) | $2.00 | $2.00 |
| Output | $14.00 | $10.00 (best) | $12.00 |
| Cached input | $0.175 (best) | $0.20 | $0.20 |
| Blended (3:1) | $4.81 | $4.00 (best) | $4.50 |
| Long-context rate | Same rate | Same rate | Over 200K: $4.00 / $18.00 |
| Price source | Official OpenAI API | Official Anthropic API | Official Google API |
| Limits | |||
| Context window | 400,000 tokens | 1,000,000 tokens | 1,048,576 tokens (best) |
| Max output | 128,000 tokens (best) | 128,000 tokens (best) | 65,536 tokens |
| Inputs and features | |||
| Text | Yes | Yes | Yes |
| Images | Yes | Yes | Yes |
| PDFs | Yes | Yes | Yes |
| Audio | No | No | Yes |
| Video | No | No | Yes |
| Reasoning | Yeslow · medium · high · xhigh | Yeslow · medium · high · xhigh · max | Yeslow · medium · high |
| Tool calling | Yes | Yes | Yes |
| Structured output | Yes | Yes | Yes |
| Availability | |||
| Weights | Proprietary | Proprietary | Proprietary |
| API model ID | gpt-5.3-codex | claude-sonnet-5 | gemini-3.1-pro-preview |
| API providers | 19 | 38 (best) | 26 |
| Released | Feb 5, 2026 | Jun 30, 2026 | Feb 19, 2026 |
| Knowledge cutoff | Aug 31, 2025 | Jan 31, 2026 | Jan 2025 |
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
- Claude Sonnet 5$40.00
- Gemini 3.1 Pro Preview$44.00
Which should you choose?
Which is better: GPT-5.3 Codex, Claude Sonnet 5 or Gemini 3.1 Pro Preview?
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, Claude Sonnet 5 or Gemini 3.1 Pro Preview?
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, Claude Sonnet 5 up to 128,000, Gemini 3.1 Pro Preview up to 65,536 tokens.
Which can read images, PDFs, audio or video?
GPT-5.3 Codex accepts text, images and PDFs; Claude Sonnet 5 accepts text, images and PDFs; Gemini 3.1 Pro Preview accepts text, images, PDFs, audio and video. Gemini 3.1 Pro Preview handles the widest range of inputs.
Are any of these open source?
No. GPT-5.3 Codex, Claude Sonnet 5 and Gemini 3.1 Pro Preview 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, Claude Sonnet 5 Jan 31, 2026, Gemini 3.1 Pro Preview Jan 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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