Gemini 3 Pro vs GPT-5.3-Codex
Gemini 3 Pro (2025) and GPT-5.3-Codex (2026) are agentic coding models from Google DeepMind and OpenAI. Gemini 3 Pro ships a 1M-token context window, while GPT-5.3-Codex ships a 400K-token context window. On SWE-bench Pro, GPT-5.3-Codex leads by 14.3 pts. On pricing, Gemini 3 Pro costs $1.25/1M input tokens versus $1.75/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit.
Gemini 3 Pro is ~40% cheaper at $1.25/1M; pay for GPT-5.3-Codex only for coding workflow support.
Decision scorecard
Local evidence first| Signal | Gemini 3 Pro | GPT-5.3-Codex |
|---|---|---|
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1M | 400K |
| Cheapest output | $5/1M tokens | $14/1M tokens |
| Provider routes | 2 tracked | 2 tracked |
| Shared benchmarks | 1 rows | SWE-bench Pro leader |
Decision tradeoffs
- Gemini 3 Pro has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Gemini 3 Pro has the lower cheapest tracked output price at $5/1M tokens.
- Gemini 3 Pro uniquely exposes Multimodal in local model data.
- Local decision data tags Gemini 3 Pro for Coding, RAG, and Agents.
- GPT-5.3-Codex leads the largest shared benchmark signal on SWE-bench Pro by 14.3 points.
- GPT-5.3-Codex uniquely exposes Reasoning and Structured outputs 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 Pro
$2,250
Cheapest tracked route: GCP Vertex AI
GPT-5.3-Codex
$4,900
Cheapest tracked route: OpenRouter
Estimated monthly gap: $2,650. Batch, cache, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for Gemini 3 Pro and GPT-5.3-Codex; plan for SDK, billing, or endpoint changes.
- GPT-5.3-Codex is $9/1M 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 and Structured outputs in local capability data.
- No overlapping tracked provider route is sourced for GPT-5.3-Codex and Gemini 3 Pro; plan for SDK, billing, or endpoint changes.
- Gemini 3 Pro is $9/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Reasoning and Structured outputs before moving production traffic.
- Gemini 3 Pro adds Multimodal in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-12-11 | 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 Pro | GPT-5.3-Codex |
|---|---|---|
| Input price | $1.25/1M tokens | $1.75/1M tokens |
| Output price | $5/1M tokens | $14/1M tokens |
| Providers |
Capabilities
| Capability | Gemini 3 Pro | GPT-5.3-Codex |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | No |
| Reasoning | No | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | No | Yes |
| Code execution | Yes | Yes |
Benchmarks
| Benchmark | Gemini 3 Pro | GPT-5.3-Codex |
|---|---|---|
| SWE-bench Pro | 42.5 | 56.8 |
Deep dive
On shared benchmark coverage, SWE-bench Pro has Gemini 3 Pro at 42.5 and GPT-5.3-Codex at 56.8, with GPT-5.3-Codex ahead by 14.3 points. The largest visible gap is 14.3 points on SWE-bench Pro, 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 Pro, reasoning mode: GPT-5.3-Codex, and structured outputs: GPT-5.3-Codex. Both models share vision, function calling, tool use, and code execution, 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 Pro lists $1.25/1M input and $5/1M 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 Pro lower by about $3.05 per million blended tokens. Availability is 2 providers versus 2, so concentration risk also matters.
Choose Gemini 3 Pro when coding workflow support, larger context windows, and lower input-token cost are central to the workload. Choose GPT-5.3-Codex when coding workflow support 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 Pro or GPT-5.3-Codex?
Gemini 3 Pro 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 Pro or GPT-5.3-Codex?
Gemini 3 Pro is cheaper on tracked token pricing. Gemini 3 Pro costs $1.25/1M input and $5/1M 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 Pro or GPT-5.3-Codex open source?
Gemini 3 Pro 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 Pro or GPT-5.3-Codex?
Both Gemini 3 Pro 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 Pro or GPT-5.3-Codex?
Gemini 3 Pro 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 Pro and GPT-5.3-Codex?
Gemini 3 Pro is available on Replicate API and GCP Vertex AI. 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.