GPT-5.5
gpt-5-5OpenAI's current flagship chat model (released April 2026). Strongest general reasoning, coding and tool use in the GPT-5 line, with vision input and a large context window.
- Price ยท 1M in / out
- US$6.00 / US$36.00
- Context
- 400,000 tokens
- Max. output
- 128,000 tokens
- Input โ output
- Text + Image โ Text
- Developer
- OpenAI
- Updated
- September 23, 2026
Playground
Try GPT-5.5
Chat
This run
at most US$0.0369 ยท 3.69 credits reserved
Billed by the tokens actually used; the unused part of the reservation is refunded.
For accounts without a purchase: runs above 2 credits need a top-up.
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Usable 24 hours after sign-up, up to 5 runs per day and at most 2 credits per run. Other sign-in methods start without credits.
About GPT-5.5
GPT-5.5 is a model by OpenAI in the Text & chat category. On Railwail, GPT-5.5 costs US$6.00 per 1M input tokens and US$36.00 per 1M output tokens. The context window holds 400,000 tokens, and one response can be up to 128,000 tokens long.
Pricing
| Input | US$6.00 / 1M tokens |
|---|---|
| Output | US$36.00 / 1M tokens |
| Input (prompts over 272,000 tokens) | US$12.00 / 1M tokens |
| Output (prompts over 272,000 tokens) | US$54.00 / 1M tokens |
- Billed by the tokens each request actually uses.
- 1 credit = US$0.01
Cost calculator
Price calculator
Total
US$2.40
240 credits
Per request
US$0.024 ยท 2.4 credits
Each request is rounded up to 0.01 credits.
API
curl https://railwail.com/api/v1/chat/completions \
-H "Authorization: Bearer $RAILWAIL_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "gpt-5-5",
"messages": [
{
"role": "user",
"content": "Explain what a vector database is in two sentences."
}
],
"max_tokens": 1024
}'import os
from openai import OpenAI
client = OpenAI(
api_key=os.environ["RAILWAIL_API_KEY"],
base_url="https://railwail.com/api/v1",
)
completion = client.chat.completions.create(
model="gpt-5-5",
messages=[
{
"role": "user",
"content": "Explain what a vector database is in two sentences.",
},
],
max_tokens=1024,
)
print(completion.choices[0].message.content)import OpenAI from "openai";
const client = new OpenAI({
apiKey: process.env.RAILWAIL_API_KEY,
baseURL: "https://railwail.com/api/v1",
});
const completion = await client.chat.completions.create({
model: "gpt-5-5",
messages: [
{
role: "user",
content: "Explain what a vector database is in two sentences."
}
],
max_tokens: 1024
});
console.log(completion.choices[0].message.content);// npm install railwail
import railwail from "railwail";
const rw = railwail(process.env.RAILWAIL_API_KEY);
const res = await rw.chat("gpt-5-5", [
{ role: "user", content: "Explain what a vector database is in two sentences." },
], { max_tokens: 1024 });
console.log(res.choices[0].message.content);Specifications
- Model ID
gpt-5-5- Developer
- OpenAI
- Category
- Text & chat
- Input
- Text, Image
- Output
- Text
- Context window
- 400,000 tokens
- Max. output
- 128,000 tokens
- Billing
- By usage (tokens or GPU time)
- Catalog entry updated
- September 23, 2026
Input parameters
Inputs and settings from the model's input schema. The example in the API section shows which of them the API accepts.
promptrequiredUser message
Type: TextDefault: โAllowed values: up to 32,000 charactersstreamType: Yes/noDefault:falseAllowed values: โmax_tokensType: IntegerDefault:4096Allowed values: 1 to 128,000system_promptOptional system instruction
Type: TextDefault: โAllowed values: up to 8,000 characters
Tags
- openai
- gpt-5
- flagship
- reasoning
- vision
- tools
Use cases
Frequently asked questions
What is GPT-5.5?
GPT-5.5 is a model by OpenAI in the Text & chat category. On Railwail you can call it with an API key through the Railwail API.
How much does GPT-5.5 cost on Railwail?
On Railwail, GPT-5.5 costs US$6.00 per 1M input tokens and US$36.00 per 1M output tokens. You are charged for what each request actually uses. Usage is paid from prepaid credits; 1 credit equals US$0.01.
What is the context window of GPT-5.5?
The context window of GPT-5.5 holds 400,000 tokens. One response can be up to 128,000 tokens long.
How fast is GPT-5.5?
There are not enough measured runs of GPT-5.5 on Railwail yet to state a run time. It depends on the input, the settings and the load at the provider.
Is GPT-5.5 better than Claude Fable 5.1?
That depends on the task. GPT-5.5 (OpenAI) and Claude Fable 5.1 (Anthropic) are both models in the Text & chat category. The comparison page shows their prices and specifications side by side.
Compare GPT-5.5 and Claude Fable 5.1Can GPT-5.5 process images?
Yes. GPT-5.5 accepts images as input in addition to text.
How do I use GPT-5.5 through the API?
Create a Railwail API key and send your request with the model ID gpt-5-5. Code examples for curl, Python and JavaScript are in the API section of this page.
Comparable models
All in this category- Claude Fable 5.1Anthropic
Anthropic's model for the most demanding reasoning and long-horizon agentic work. 1M-token context window, up to 128K output tokens, adaptive thinking that is always on.
- Claude Opus 4.8Anthropic
The most capable model of Anthropic's Opus 4 series. State of the art on long-horizon agentic work, coding and knowledge tasks, with a 1M-token context window at standard pricing.
- Claude Opus 5.5Anthropic
Anthropic's current Opus model for long-running agentic coding and knowledge work. 1M-token context window, up to 128K output tokens, adaptive thinking that is always on.
Use GPT-5.5 via the API
One API key for every model on Railwail. Usage is charged from prepaid credits, 1 credit = US$0.01.