Gemini 3.1 Pro Preview vs GPT-5.3-Codex
Gemini 3.1 Pro Preview (2026) and GPT-5.3-Codex (2026) are agentic coding models from Google DeepMind and OpenAI. Gemini 3.1 Pro Preview ships a 1M-token context window, while GPT-5.3-Codex ships a 400K-token context window. On SWE-bench Verified, GPT-5.3-Codex leads by 4.4 pts. On pricing, GPT-5.3-Codex costs $1.75/1M input tokens versus $2/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit.
Pick GPT-5.3-Codex for coding; Gemini 3.1 Pro Preview is better when coding workflow support matters more.
Decision scorecard
Local evidence first| Signal | Gemini 3.1 Pro Preview | GPT-5.3-Codex |
|---|---|---|
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1M | 400K |
| Cheapest output | $12/1M tokens | $14/1M tokens |
| Provider routes | 4 tracked | 2 tracked |
| Shared benchmarks | 3 rows | SWE-bench Verified leader |
Decision tradeoffs
- Gemini 3.1 Pro Preview has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Gemini 3.1 Pro Preview has the lower cheapest tracked output price at $12/1M tokens.
- Gemini 3.1 Pro Preview has broader tracked provider coverage for fallback and procurement flexibility.
- Gemini 3.1 Pro Preview uniquely exposes Multimodal in local model data.
- Local decision data tags Gemini 3.1 Pro Preview for Coding, RAG, and Agents.
- GPT-5.3-Codex leads the largest shared benchmark signal on SWE-bench Verified by 4.4 points.
- GPT-5.3-Codex uniquely exposes Reasoning in local model data.
- Local decision data tags GPT-5.3-Codex for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output prices on this page.
Gemini 3.1 Pro Preview
$4,600
Cheapest tracked route: Google AI Studio
GPT-5.3-Codex
$4,900
Cheapest tracked route: OpenRouter
Estimated monthly gap: $300. Batch, cache, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- GPT-5.3-Codex is $2/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Check replacement coverage for Multimodal before moving production traffic.
- GPT-5.3-Codex adds Reasoning in local capability data.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Gemini 3.1 Pro Preview is $2/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Reasoning before moving production traffic.
- Gemini 3.1 Pro Preview adds Multimodal in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-02-19 | 2026-02-05 |
| Context window | 1M | 400K |
| Parameters | — | — |
| Architecture | decoder only | decoder only |
| License | Proprietary | Proprietary |
| Knowledge cutoff | 2025-01 | 2025-08 |
Pricing and availability
| Pricing attribute | Gemini 3.1 Pro Preview | GPT-5.3-Codex |
|---|---|---|
| Input price | $2/1M tokens | $1.75/1M tokens |
| Output price | $12/1M tokens | $14/1M tokens |
| Providers |
Capabilities
| Capability | Gemini 3.1 Pro Preview | GPT-5.3-Codex |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | No |
| Reasoning | No | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | Yes |
Benchmarks
| Benchmark | Gemini 3.1 Pro Preview | GPT-5.3-Codex |
|---|---|---|
| SWE-bench Verified | 80.6 | 85.0 |
| SWE-bench Pro | 54.2 | 56.8 |
| τ-bench | 76.5 | 77.8 |
Deep dive
On shared benchmark coverage, SWE-bench Verified has Gemini 3.1 Pro Preview at 80.6 and GPT-5.3-Codex at 85, with GPT-5.3-Codex ahead by 4.4 points; SWE-bench Pro has Gemini 3.1 Pro Preview at 54.2 and GPT-5.3-Codex at 56.8, with GPT-5.3-Codex ahead by 2.6 points; τ-bench has Gemini 3.1 Pro Preview at 76.5 and GPT-5.3-Codex at 77.8, with GPT-5.3-Codex ahead by 1.3 points. The largest visible gap is 4.4 points on SWE-bench Verified, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint differs most on multimodal input: Gemini 3.1 Pro Preview and reasoning mode: GPT-5.3-Codex. Both models share vision, function calling, tool use, and structured outputs, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, Gemini 3.1 Pro Preview lists $2/1M input and $12/1M output tokens, while GPT-5.3-Codex lists $1.75/1M input and $14/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Gemini 3.1 Pro Preview lower by about $0.42 per million blended tokens. Availability is 4 providers versus 2, so concentration risk also matters.
Choose Gemini 3.1 Pro Preview when coding workflow support, larger context windows, and broader provider choice are central to the workload. Choose GPT-5.3-Codex when coding workflow support and lower input-token cost are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship.
FAQ
Which has a larger context window, Gemini 3.1 Pro Preview or GPT-5.3-Codex?
Gemini 3.1 Pro Preview supports 1M tokens, while GPT-5.3-Codex supports 400K tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Which is cheaper, Gemini 3.1 Pro Preview or GPT-5.3-Codex?
GPT-5.3-Codex is cheaper on tracked token pricing. Gemini 3.1 Pro Preview costs $2/1M input and $12/1M output tokens. GPT-5.3-Codex costs $1.75/1M input and $14/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Gemini 3.1 Pro Preview or GPT-5.3-Codex open source?
Gemini 3.1 Pro Preview is listed under Proprietary. GPT-5.3-Codex is listed under Proprietary. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for vision, Gemini 3.1 Pro Preview or GPT-5.3-Codex?
Both Gemini 3.1 Pro Preview and GPT-5.3-Codex expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, Gemini 3.1 Pro Preview or GPT-5.3-Codex?
Gemini 3.1 Pro Preview has the clearer documented multimodal input signal in this comparison. If multimodal input is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run Gemini 3.1 Pro Preview and GPT-5.3-Codex?
Gemini 3.1 Pro Preview is available on Google AI Studio, GCP Vertex AI, OpenRouter, and Replicate API. GPT-5.3-Codex is available on OpenRouter and OpenAI API. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-05-11. Data sourced from public model cards and provider documentation.