GPT-5.5 Pro
Access GPT-5.5 Pro through one API key. OpenAI's most powerful reasoning model.
OpenAI's most powerful reasoning model. GPT-5.5 Pro is tuned for the hardest analytical, scientific, and coding problems where maximum accuracy matters more than cost.
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-5.5 Pro respond in real time.
Maximum tokens in the response.
Real-time tokens
Context Window
1.1M tokens
Max Output
33K tokens
Input Price
$42.00 / 1M tokens
Output Price
$252.00 / 1M tokens
Strengths
GPT-5.5 Pro is tuned for maximum accuracy on the hardest problems, trading cost and speed for top-tier correctness.
Reads up to 1,050,000 tokens per request, so it can reason over entire codebases or large document sets without losing context.
Built for long, careful chains of reasoning on analytical, scientific, and mathematical problems where accuracy matters most.
Targets the toughest engineering and analytical work, returning up to 32,768 output tokens for thorough solutions.
Quick start
Copy this snippet and start making calls with GPT-5.5 Pro.
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-5.5-pro",
"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-5.5 Pro through YepAPI?
GPT-5.5 Pro API — pricing, context window & access
GPT-5.5 Pro is OpenAI's most powerful reasoning model, tuned for the hardest analytical, scientific, and coding problems where maximum accuracy matters more than cost. It carries a 1,050,000-token context window and up to 32,768 output tokens per response.
Through YepAPI you call GPT-5.5 Pro on an OpenAI-compatible endpoint with one key — the same key that also reaches GPT-5.5, the GPT-5.4 family, Claude, Gemini, and the SEO, SERP and scraping endpoints.
What is GPT-5.5 Pro?
GPT-5.5 Pro is OpenAI's most powerful reasoning model — the maximum-accuracy variant above the standard GPT-5.5 flagship. It's purpose-built for the hardest problems: rigorous mathematics, scientific analysis, and the most demanding coding, where being right matters far more than being fast or cheap. It keeps the 1,050,000-token context window of the GPT-5.5 line, letting it hold huge inputs while it reasons through them in depth. This is the model you reserve for the few tasks that justify top-tier cost in exchange for the best correctness OpenAI offers.
Build with GPT-5.5 Pro via YepAPI
YepAPI exposes GPT-5.5 Pro through the OpenAI-compatible /v1/ai/chat endpoint, so you call it with the chat-completions format and the model string gpt-5.5-pro. Because it reasons deeply, expect longer, more expensive responses — and switch down to GPT-5.5 or GPT-5.4 for everyday work with a one-string change. The same key also covers search and scraping endpoints, so your hardest-problem calls and your data pipelines run on a single account.
GPT-5.5 Pro API pricing — $42.00 / 1M input, $252.00 / 1M output
GPT-5.5 Pro costs $42.00 per 1M input tokens and $252.00 per 1M output tokens through YepAPI — premium pricing for premium accuracy. At these rates it's strictly an escalation tier: use it for the small set of problems where a wrong answer is costly and route everything else to cheaper models. Deep reasoning means heavier output, so the output rate dominates total cost. You pay only for tokens used, with no minimums.
GPT-5.5 Pro for the hardest reasoning
GPT-5.5 Pro is the model for problems that defeat everything else. On rigorous proofs, scientific analysis, and intricate engineering tasks, its deep multi-step reasoning works through long chains carefully rather than rushing to an answer. The 1M-token window lets it keep an entire problem — codebase, dataset, or paper — in view while it reasons. Treat it as the final escalation when maximum accuracy justifies the cost.
Try GPT-5.5 Pro free
New YepAPI accounts get $5 in free credit, no card required. That's enough to point GPT-5.5 Pro at one genuinely hard problem and judge the quality for yourself. Sign up, grab your key, and start calling GPT-5.5 Pro in minutes.
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 most powerful reasoning model. GPT-5.5 Pro is tuned for the hardest analytical, scientific, and coding problems where maximum accuracy matters more than cost.
Input tokens cost $42.00 per 1M tokens and output tokens cost $252.00 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/chat endpoint.
GPT-5.5 Pro supports a 1.1M token context window with up to 33K output tokens per request.
Ready to use GPT-5.5 Pro?
$5 free credit on signup. No credit card required. Pay per call.
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