GPT-5.3 Codex API

GPT-5.3 Codex is a coding-specialized model from the GPT-5.3 series for advanced code generation.
Context
400K tokens
Input
$2.275 / 1M
Output
$18.2 / 1M
Released
Mar 2, 2026

How to use GPT-5.3 Codex API

Install any OpenAI-compatible SDK, point it at api.aimlapi.com/v1, and set the model to openai/gpt-5.3-codex.
import requests

r = requests.post(
    "https://api.aimlapi.com/v1/chat/completions",
    headers={"Authorization": "Bearer " + AIMLAPI_KEY},
    json={
      "model": "openai/gpt-5.3-codex",
      "messages": [
        {
          "role": "user",
          "content": "Hello!"
        }
      ]
    },
)
print(r.json())
const r = await fetch("https://api.aimlapi.com/v1/chat/completions", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.AIMLAPI_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "model": "openai/gpt-5.3-codex",
    "messages": [
      {
        "role": "user",
        "content": "Hello!"
      }
    ]
  }),
});
console.log(await r.json());
curl -X POST https://api.aimlapi.com/v1/chat/completions \
  -H "Authorization: Bearer $AIMLAPI_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model":"openai/gpt-5.3-codex","messages":[{"role":"user","content":"Hello!"}]}'

OpenAI-compatible — swap the base URL and it works with your existing SDK.

GPT-5.3 Codex API Pricing

TypePrice
Input
$2.275 / 1M tokens
Output
$18.2 / 1M tokens

GPT-5.3 Codex Benchmarks

BenchmarkScoreWhat it measures
OSWorld
64.7%
Computer-use across real desktop applications
Terminal-Bench
77.3%
Autonomous shell/terminal task completion

GPT-5.3 Codex vs other models

ModelInputOutputContextBest for
GPT-5.3 Codex
This page
$2.275 / 1M
$18.2 / 1M
400K tokens
Reasoning + agents
$6.5 / 1M
$39 / 1M
1.05M tokens
Reasoning + agents
$2.6 / 1M
$13 / 1M
1M tokens
Balanced coding + agents
$3.9 / 1M
$19.5 / 1M
1M tokens
Long-context, multimodal & agentic workflows
$0.65 / 1M
$3.9 / 1M
1.05M tokens
Reasoning + agents

Start building with GPT-5.3 Codex

Get API Key
1000+ models, one API.