GPT-5.3 Codex vs GPT-5
Compare GPT-5.3 Codex and GPT-5. Build AI products powered by either model on Appaca.
Model Comparison
| Feature | GPT-5.3 Codex | GPT-5 |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Model Type | text | text |
| Context Window | 400,000 tokens | 400,000 tokens |
| Input Cost | $1.75/ 1M tokens | $1.25/ 1M tokens |
| Output Cost | $14.00/ 1M tokens | $10.00/ 1M tokens |
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Strengths & Best Use Cases
GPT-5.3 Codex
OpenAI1. 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.
GPT-5
OpenAI1. High reasoning capability
- Designed for intelligent reasoning across complex domains.
- Supports reasoning tokens and adjustable reasoning effort.
2. Strong coding and agentic performance
- Optimized for multi-step coding tasks, tool-use chains, and agent workflows.
- Handles complex logic, planning, and structured problem solving reliably.
3. Multimodal input
- Accepts text + image as input.
- Produces text outputs with strong instruction following.
4. Extensive tool support
- Works with Web Search, File Search, Image Generation (as a tool), Code Interpreter, MCP, and more.
- Integrated across Chat Completions, Responses API, Realtime, Assistants, Batch, Embeddings, etc.
Prompts to Get Started
Use these prompts to power AI products you build on Appaca. Each works great with the models above.
Best for GPT-5.3 Codex
textBug Fixer & Debugger
Identify bugs in your code, understand why they happen, and get a corrected version.
Cold Outreach Email Generator
Generate high-converting cold emails for sales, networking, or partnerships.
Professional Email Rewriter
Rewrite your rough drafts into polished, professional emails suitable for any business context.
Best for GPT-5
textNeighborhood Guide Content Creator (Local Expert Blog)
Outline a high-value neighborhood guide blog post that positions you as the local expert with sections for food, parks/schools, vibe, and commute.
Formative Assessment Ideas Generator
Generate diverse formative assessment strategies that check for understanding throughout a lesson without formal testing.
Develop Debt Payoff Strategy
Guide users to financial freedom with this AI prompt, combining financial analysis and psychological insight for personalized debt elimination strategies.