GPT-5.5 vs GPT-5.6

As of November 10, 2026, GPT-5.5 costs 25% more per input token than GPT-5.6 ($5.00 vs $4.00 per 1M) and has a 1M-token context window versus 922K.

Prices from LiteLLM's price fileChecked November 10, 2026

GPT-5.5 vs GPT-5.6 side by side

Headline prices in US dollars per 1M tokens: each model's own lab where it sells it, otherwise its cheapest provider. Source: LiteLLM model price file, as of November 10, 2026.
	GPT-5.5	GPT-5.6
Input, per 1M tokens	$5.00	$4.00
Output, per 1M tokens	$30.00	$20.00
Cache read, per 1M tokens	$0.50	$0.40
Cache write, per 1M tokens	–	$5.00
Context window	1,050,000 tokens	922,000 tokens
Max output	128,000 tokens	128,000 tokens
Image input	Yes	Yes
Tool calling	Yes	Yes
Structured output (JSON)	Yes	Yes
Prompt caching	Yes	Yes
Reasoning	Yes	Yes
Providers on LiteLLM	11	2
Price shown is from	OpenAI	OpenAI
Added to LiteLLM	April 2026	July 9, 2026

Cheapest provider for each

GPT-5.5: OpenAI at $5.00 input and $30.00 output per 1M tokens (gpt-5.5)
GPT-5.6: OpenAI at $4.00 input and $20.00 output per 1M tokens (gpt-5.6)

When to pick which

Pick GPT-5.5 for

Larger context window: 1,050,000 vs 922,000 tokens.
Available from 11 providers through LiteLLM, vs 2.

Pick GPT-5.6 for

Costs 20% less per input token: $4.00 vs $5.00 per 1M.

From differences in the data above only; where the data is equal, no reason is given.

Call GPT-5.5 or GPT-5.6 with LiteLLM

Both use the OpenAI format through LiteLLM, so switching is a model name change. Set each provider's API key in the environment first.

Python SDK

from litellm import completion

messages = [{"role": "user", "content": "Hello!"}]

# GPT-5.5
response = completion(model="gpt-5.5", messages=messages)

# GPT-5.6
response = completion(model="gpt-5.6", messages=messages)

# GPT-5.5, falling back to GPT-5.6 if the call fails
response = completion(model="gpt-5.5", messages=messages, fallbacks=["gpt-5.6"])

FAQ

Which is cheaper, GPT-5.5 or GPT-5.6?

GPT-5.6 is cheaper at 3 input tokens per output token: $8.00 per 1M tokens blended ($4.00 input, $20.00 output), versus $11.25 ($5.00 and $30.00) for GPT-5.5, as of November 10, 2026.

Which has the larger context window, GPT-5.5 or GPT-5.6?

GPT-5.5 has the larger context window: 1,050,000 tokens, versus 922,000 for GPT-5.6.

Can I switch from GPT-5.5 to GPT-5.6 without changing my code?

Yes. Through LiteLLM both use the OpenAI format, so switching means changing the model name from "gpt-5.5" to "gpt-5.6", or pointing a LiteLLM gateway model alias at the other model. You can also use one as a fallback for the other.