GPT-5.5

GPT-5.5 is the OpenAI model for coding and professional work released on April 23, 2026, and it is still offered as a pinned snapshot in the API. It has a 1.05M-token context window and reasoning effort from none to xhigh.

By OpenAIReleased April 23, 2026Data checked October 10, 2026

LegacyClosedFrontier

Specifications

Context window: 1.05Mabout 788,000 words, or 1,580 pages
Max output: 125Ktokens per response
Input price: $5per 1M tokens
Output price: $30per 1M tokens
Cached input: $0.50per 1M tokens
Weights: ClosedProprietary
Parameters: Undisclosed
Input types: Text, Images
Output types: Text
Reasoning mode: Yes
Tool calling: Yes
Released: Apr 23, 2026Legacy

Prompts over 272K input tokens cost 2x input and 1.5x output for the session. Regional processing adds 10%.

What it costs in practice

Workload	Monthly cost at list price
Support chatbot30,000 conversations a month, 2,000 input and 400 output tokens each	$660
Document summaries2,000 documents a month, 12,000 input and 800 output tokens each	$168
Coding agent1,000 tasks a month, 60,000 input and 6,000 output tokens each	$480

Standard rates, no caching or batch discounts. Run your own numbers.

Strengths

1.05M-token context window and 128K-token output limit
Pinned snapshot (gpt-5.5-2026-04-23) for consistent behavior
Reasoning can be switched off with the none setting

Trade-offs to weigh

$5 input and $30 output per million tokens, more than GPT-6.1 Sol
Knowledge cutoff of December 1, 2025

Where it fits

OpenAI positions GPT-5.5 for:

codingagentswritingreasoning

Where you can use it

API
OpenRouter

Alternatives to consider

Model	Tier	Context	Input / output per 1M
Claude Opus 5.5Anthropic	Frontier	1M	$4 / $20	Compare
Claude Fable 5.1Anthropic	Frontier	1M	$10 / $50	Compare
Gemini 3.1 ProGoogle	Frontier	1M	$2 / $12	Compare
Kimi K3Moonshot AI	Frontier	1M	$3 / $15	Compare

Frequently asked questions

How much does GPT-5.5 cost?

GPT-5.5 lists at $5 per million input tokens and $30 per million output tokens, with cached input at $0.50 (checked October 10, 2026). Prompts over 272K input tokens cost 2x input and 1.5x output for the session. Regional processing adds 10%. Confirm current rates on the provider's pricing page before you commit.

What is the context window of GPT-5.5?

GPT-5.5 accepts up to 1,050,000 tokens of context (about 788,000 words, or 1,580 pages), and it can write up to 125K tokens in a single response. Long prompts cost more and can be slower, so most apps send only what the task needs.

Is GPT-5.5 open source?

No. GPT-5.5 is a proprietary model from OpenAI; its weights aren't published. You can use it through the OpenAI API and through OpenRouter.

What is GPT-5.5 best for?

OpenAI positions GPT-5.5 for coding, agents, writing, reasoning. It accepts text, images as input, has a reasoning (thinking) mode and supports tool calling. Test it on a sample of your own tasks before you choose it for production.

Sources

Facts checked against these pages on October 10, 2026. Spot an error? Tell us.

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