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.
No credit card required. Takes 30 seconds.
2,400+
Developers
1.2M+
API calls served
100+
Endpoints
$0.01
Per call
Yep, that's it.
Try it live
Send a message and see GPT-5.3 Codex respond in real time.
Maximum tokens in the response.
Real-time tokens
Context Window
400K tokens
Max Output
128K tokens
Input Price
$2.45 / 1M tokens
Output Price
$19.60 / 1M tokens
Strengths
GPT-5.3 Codex is OpenAI's previous-generation coding model, tuned for code generation, refactoring, and software engineering tasks.
A 400,000-token context window lets it ingest large multi-file codebases and long histories before suggesting changes.
Up to 128,000 output tokens per response means it can generate entire files, modules, or large refactors in one call.
The combination of 400K context and 128K output suits repo-scale work like migrations and full-feature scaffolding.
Quick start
Copy this snippet and start making calls with GPT-5.3 Codex.
const res = await fetch('https://api.yepapi.com/v1/ai/chat', {
method: 'POST',
headers: {
'x-api-key': 'YOUR_API_KEY',
'Content-Type': 'application/json',
},
body: JSON.stringify({
"model": "openai/gpt-5.3-codex",
"messages": [
{
"role": "user",
"content": "Explain API gateways in 2 sentences."
}
],
"maxTokens": 256
}),
});
const { data } = await res.json();
console.log(data.message.content);Why use GPT-5.3 Codex through YepAPI?
GPT-5.3 Codex API: previous-gen coding model with massive output
GPT-5.3 Codex is OpenAI's previous-generation coding model, pairing a 400K-token context window with up to 128K output tokens for large code tasks. At $2.45 per 1M input tokens and $19.60 per 1M output tokens, it is a capable, lower-cost option for repo-scale generation and refactoring.
Through YepAPI you reach GPT-5.3 Codex with a single OpenAI-compatible API key. That key also unlocks other models and YepAPI's SEO, SERP, and web-scraping endpoints, so you can generate code and gather data in one account.
What is GPT-5.3 Codex?
GPT-5.3 Codex is OpenAI's previous-generation coding-specialized model, built for code generation, refactoring, and broader software engineering. It stands out for scale: a 400,000-token context window lets it read large multi-file codebases, and up to 128,000 output tokens per response let it emit entire files or sweeping refactors in a single call. That makes it well suited to repo-scale tasks rather than just snippets. As a prior-generation release it costs $2.45 per 1M input and $19.60 per 1M output tokens, offering strong coding capability at a lower price than the current flagship coders.
Build with GPT-5.3 Codex via YepAPI
Call the OpenAI-compatible /v1/ai/chat endpoint with your YepAPI key. The Chat Completions schema means existing SDKs and coding agents work after changing the base URL and model name. Use it for large refactors, migrations, and full-feature scaffolding where the 128K output is decisive. One key also covers other models plus SEO, SERP, and scraping APIs, so a coding agent can both write code and pull reference data from the web through a single integration.
GPT-5.3 Codex API pricing — $2.45 / $19.60 per 1M tokens
GPT-5.3 Codex costs $2.45 per 1M input tokens and $19.60 per 1M output tokens. Because it can emit up to 128K tokens at once, output pricing matters for big generations, but the previous-generation rate keeps repo-scale tasks affordable. Billing is per token, so reading a large codebase and producing a substantial refactor is priced predictably by volume.
GPT-5.3 Codex for repo-scale refactoring
The model is built for large coding jobs: migrating a service to a new framework, refactoring across many files, or scaffolding a complete feature with tests. The 400K context lets it understand a whole module and its dependencies, while the 128K output ceiling means it can return the entire result in one pass instead of fragmenting it. That makes it a strong engine for automated, large-scale code transformation.
Try GPT-5.3 Codex free
New YepAPI accounts include $5 in free credit with no card required. That is enough to run real refactoring and generation tasks with GPT-5.3 Codex against your own repository before you commit to it.
Start generating in 30 seconds
$5 free credit on signup. No credit card required. Pay per call.
What developers say
“Switched from SerpAPI and cut our SERP costs by 80%. Same data quality, way simpler billing.”
“One API key for AI models, SERP data, and web scraping. Saved us from managing 4 separate providers.”
“The $5 free credit let us prototype our entire rank tracking feature before committing. No other API does that.”
Frequently asked questions
OpenAI's previous generation coding model. 400K context and 128K output tokens for large code tasks.
Input tokens cost $2.45 per 1M tokens and output tokens cost $19.60 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/chat endpoint.
GPT-5.3 Codex supports a 400K token context window with up to 128K output tokens per request.
Ready to use GPT-5.3 Codex?
$5 free credit on signup. No credit card required. Pay per call.
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