GPT-5.3 Codex vs Gemini 3 Pro
Compare pricing, context windows, and strengths for GPT-5.3 Codex by OpenAI and Gemini 3 Pro by Google - and see how to put either to work in Appaca.
GPT-5.3 Codex
Most capable agentic coding model to date, optimized for long-horizon software engineering tasks with configurable reasoning and multimodal input.
View GPT-5.3 CodexGemini 3 Pro
Google's most intelligent multimodal model designed for advanced reasoning, coding, and agentic tasks.
View Gemini 3 ProGPT-5.3 Codex vs Gemini 3 Pro at a glance
Specs and pricing side by side, from the Appaca AI models directory.
| Spec | GPT-5.3 Codex | Gemini 3 Pro |
|---|---|---|
| Provider | OpenAI | |
| Model type | Text | Text |
| Context window | 400K tokens | 1M tokens |
| Input price | $1.75 / 1M tokens | $4 / 1M tokens |
| Output price | $14 / 1M tokens | $18 / 1M tokens |
| Status | Current | Superseded by Gemini 3.1 Pro |
How GPT-5.3 Codex and Gemini 3 Pro differ
What the numbers mean in practice when choosing between GPT-5.3 Codex and Gemini 3 Pro.
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GPT-5.3 Codex is 56% cheaper on input tokens ($1.75 vs $4 per million), which adds up quickly in document-heavy workloads.
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GPT-5.3 Codex is 22% cheaper on output tokens ($14 vs $18 per million) - the bigger factor for tools that generate long documents.
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Gemini 3 Pro's 1M tokens context window is roughly 2.5x larger than GPT-5.3 Codex's 400K tokens, so it can work across bigger codebases, contracts, or archives in one pass.
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Gemini 3 Pro has been superseded by Gemini 3.1 Pro - for new builds, consider the newer model first.
Strengths side by side
Where each model shines, according to benchmarks and provider positioning.
GPT-5.3 Codex
1. Strongest Codex Model for Agentic Engineering
- OpenAI positions GPT-5.3 Codex as its most capable agentic coding model to date.
- Built for long-horizon software engineering tasks that require planning, iteration, and reliable code transformation across files.
2. Configurable Reasoning + Multimodal Input
- Supports configurable reasoning effort from low to xhigh so teams can trade off depth against latency.
- Accepts both text and image inputs while producing text output.
3. Large Context for Real Codebases
- 400 k token context window helps it work across larger repositories, implementation plans, and supporting documentation.
- Allows up to 128 k output tokens for longer code generations, patches, and technical write-ups.
4. Current Knowledge for Modern Dev Workflows
- Knowledge cut-off of Aug 31 2025 keeps it aligned with newer frameworks, libraries, and tooling.
- Supports streaming, function calling, and structured outputs for agent-style coding workflows.
Gemini 3 Pro
1. State-of-the-art reasoning
- Top performance across academic reasoning, scientific knowledge, math, and complex problem-solving.
- Excels at long-horizon, multi-step workflows and deep logical interpretation.
2. World-leading multimodal capabilities
- Natively understands text, images, videos, audio, and code.
- Ranked highest on benchmarks like MMMU-Pro, Video-MMMU, ScreenSpot-Pro.
3. Exceptional coding + agentic workflows
- Strong in competitive coding and real-world agentic tasks (SWE-Bench Verified, Terminal-Bench, LiveCodeBench).
- Improved tool calling, planning, and execution for autonomous or semi-autonomous agents.
4. Powerful for long-context tasks
- Effective at 128K-1M context windows with high retrieval accuracy.
- Ideal for document-heavy workflows, research, analysis, multi-file coding, and multi-document reasoning.
5. Strong information synthesis and interpretation
- Outperforms peers in chart reasoning, OCR, structured extraction, and screen understanding.
- Excellent at combining multimodal inputs into coherent, concise answers.
6. High reliability for enterprise tasks
- Benchmarks show superior factuality, grounding, and parametric knowledge.
- Strong multilingual accuracy and global commonsense performance.
7. Optimized for production agents
- Designed for complex multi-step planning, simultaneous task execution, and improved consistency.
- Works across coding, research, creative workflows, UI generation, and data-heavy applications.
Use GPT-5.3 Codex or Gemini 3 Pro - or both
Appaca is the AI workspace for operators. Build internal tools and AI co-workers powered by GPT-5.3 Codex or Gemini 3 Pro - connected to your real data and ready for your whole team. No code, no deployment.
Describe it, and it's built
Tell the Appaca agent the internal tool you need and it builds a working app powered by GPT-5.3 Codex or Gemini 3 Pro. No code, no API keys, no deployment.
Switch models without rebuilding
Start on GPT-5.3 Codex, test the same tool on Gemini 3 Pro, and keep whichever performs better - the rest of your app stays exactly as it is.
Automated for the whole team
Schedule tools to run on autopilot - daily digests, weekly reports, real-time triggers - and share them with your whole team from one workspace.
Describe it, and it's built
Tell the Appaca agent what your team needs and it builds a working app powered by GPT-5.3 Codex or Gemini 3 Pro - connected to the tools you already use.
Related comparisons
See how GPT-5.3 Codex and Gemini 3 Pro stack up against other models in the directory.
FAQs
GPT-5.3 Codex is generally cheaper: $1.75 input / $14 output per million tokens, versus $4 / $18 for Gemini 3 Pro. Actual cost depends on how many tokens your workload reads and writes.
Gemini 3 Pro has the larger context window at 1M tokens, compared to 400K tokens for GPT-5.3 Codex. A larger window means the model can consider more text at once - useful for long contracts, codebases, or months of records.
It depends on the job. Compare the pricing, context window, and strengths above against your workload - and remember the choice isn't permanent. In Appaca you can build a tool on GPT-5.3 Codex, test the same tool on Gemini 3 Pro, and switch at any time without rebuilding anything.
Yes. Appaca is a no-code AI workspace: describe the internal tool your team needs and the Appaca agent builds it as a working app powered by GPT-5.3 Codex, Gemini 3 Pro, or any other model in the directory - with a built-in database, team access, and integrations. No API keys to wire up and nothing to deploy.
Build AI tools with GPT-5.3 Codex or Gemini 3 Pro
Describe the tool your team needs and get a working app powered by the model you choose - with a built-in database, team access, and integrations. No code, no deployment.