GPT-5.3-Codex
VerifiedMultimodal coding model with 400k-token context from OpenAI.
About GPT-5.3-Codex
Developed by OpenAI, GPT-5.3-Codex combines multimodal input handling with an extensive context capacity. This design supports simultaneous analysis of code, documentation, and visual elements. Access remains restricted to API usage under OpenAI's controlled release.
Its strengths lie in managing large-scale projects that mix textual instructions with image-based references or file uploads. Developers commonly apply it to code generation, debugging, and refactoring tasks. Integration into IDEs or documentation pipelines forms a typical usage pattern.
Capabilities
How GPT-5.3-Codex compares
GPT-5.3-Codex (striped bar) vs other multimodal on intelligence, speed and price.
Price
USD per 1M output tokens · Lower is better · GPT-5.3-Codex ranks #45 of 63
Sources: Artificial Analysis (intelligence, speed) · OpenRouter (price).
Best for
Large-Scale Codebase Analysis
The 400,000-token context enables processing and refactoring of entire repositories or multi-file projects without losing coherence across distant sections of code.
Multimodal Software Prototyping
It interprets diagrams, UI screenshots, and handwritten notes together with code to generate or debug implementations that match visual specifications.
Long-Context Technical Documentation
The model maintains consistency when creating or updating extensive API references, architecture docs, and inline comments spanning hundreds of thousands of tokens.
Strengths & limitations
Strengths
- +Specialized for programming workflows
- +Extensive context handling
- +Support for diverse input types
Limitations
- –Narrower focus than general-purpose models
- –Performance tied to input quality
Cost calculator
Estimate what GPT-5.3-Codex would cost for your usage.
Based on GPT-5.3-Codex's $1.75/1M input · $14.00/1M output. Estimate only — actual cost varies by provider and caching.
Quick start
OpenRouter's API is OpenAI-compatible — most SDKs work by just swapping the base URL. Only the model slug changes between models.
import OpenAI from "openai";
const client = new OpenAI({
baseURL: "https://openrouter.ai/api/v1",
apiKey: process.env.OPENROUTER_API_KEY,
});
const completion = await client.chat.completions.create({
model: "openai/gpt-5.3-codex",
messages: [{ role: "user", content: "Hello!" }],
});
console.log(completion.choices[0].message.content);Model slug: openai/gpt-5.3-codex
Editor's verdict
GPT-5.3-Codex is OpenAI's proprietary multimodal with a 400K-token context window.
At $14.00 per 1M output tokens, it is premium-priced for its class.
It is available through OpenAI's API and aggregators like OpenRouter.
Best suited to specialized for programming workflows and extensive context handling.
Frequently asked questions
The model supports a context length of 400,000 tokens.
User reviews
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