OpenAI/v1/ai/openai/gpt-5.3-codex

GPT-5.3 Codex

Access GPT-5.3 Codex through one API key. Previous-gen coding model with massive output.

OpenAI's previous generation coding model. 400K context and 128K output tokens for large code tasks.

Full Docs Get API Key

Context Window

400K tokens

Max Output

128K tokens

Input Price

$1.75 / 1M tokens

Output Price

$14.00 / 1M tokens

Try it live

Send a message and see GPT-5.3 Codex respond in real time.

POST /v1/ai/openai/gpt-5.3-codexLive testing

API Key

Message *

Max Tokens

Maximum tokens in the response.

Stream

Real-time token streaming

Hit "Run" to see the response

Strengths

✓Coding specialist

✓400K context

✓128K output

✓Large codebase tasks

Quick start

Copy this snippet and start making calls with GPT-5.3 Codex.

const res = await fetch('https://api.yepapi.com/v1/ai/openai/gpt-5.3-codex', {
  method: 'POST',
  headers: {
    'x-api-key': 'YOUR_API_KEY',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    "messages": [
      {
        "role": "user",
        "content": "Explain API gateways in 2 sentences."
      }
    ],
    "maxTokens": 256
  }),
});
const data = await res.json();
console.log(data);

Why use GPT-5.3 Codex through YepAPI?

✓One API key for all models — no separate accounts

✓OpenAI SDK compatible — just change the base URL

✓No monthly minimums — pay per token

✓Switch models with one line of code

✓Full provider passthrough — citations, search results, and all extras included

✓Streaming and non-streaming support on every model

✓Works with Cursor, Claude, LangChain, and any LLM tool

✓Unified billing across all providers

Frequently asked questions

OpenAI's previous generation coding model. 400K context and 128K output tokens for large code tasks.

Input tokens cost $1.75 per 1M tokens and output tokens cost $14.00 per 1M tokens through YepAPI. No monthly minimums — you only pay for what you use.

Sign up for a free API key, then send requests to the /v1/ai/openai/gpt-5.3-codex endpoint. YepAPI is OpenAI SDK compatible, so you can use it with any tool that supports OpenAI — just change the base URL.

GPT-5.3 Codex supports a 400K token context window with up to 128K output tokens per request.