Question 1

What does this GPT-5 Nano vs GPT-Realtime-2.1 comparison cover?

Accepted Answer

It brings together documented inputs and outputs, token limits, deployment terms and available pricing. When both models have source-linked, verified results on a shared benchmark, those results are shown with their individual sources. The comparison is a starting point for evaluating your own workload.

Question 2

Which is cheaper: GPT-5 Nano or GPT-Realtime-2.1?

Accepted Answer

GPT-5 Nano lists $0.05 input and $0.40 output per 1M tokens. GPT-Realtime-2.1 lists $4.00 input and $24.00 output. The cheaper workload depends on the mix of input and output. Long-context tiers, caching, batch processing and retries can change the bill.

Question 3

Which has the larger context window: GPT-5 Nano or GPT-Realtime-2.1?

Accepted Answer

GPT-5 Nano lists 400K tokens and GPT-Realtime-2.1 lists 128K. GPT-5 Nano therefore has the larger recorded context window, but capacity alone is not a quality score.

Question 4

Which is faster: GPT-5 Nano or GPT-Realtime-2.1?

Accepted Answer

There is no matched speed measurement for both models with the same source, host, region and date. Test the same prompts at your expected concurrency and measure time to the first useful response as well as complete task time.

Question 5

What input and output types do GPT-5 Nano and GPT-Realtime-2.1 support?

Accepted Answer

GPT-5 Nano records text, image input and text output. GPT-Realtime-2.1 records text, audio, image input and text, audio output. “Not documented” means the current source record is incomplete; it does not prove that a modality is unsupported.

Question 6

Should I choose GPT-5 Nano or GPT-Realtime-2.1?

Accepted Answer

Consider GPT-5 Nano if you need larger context or larger maximum output or a lower listed input rate or a lower listed output rate. Test both on the same representative examples and judge the output against your acceptance criteria. Include tool failures, retries and the time to a completed task.

Specification	GPT-5 Nano	GPT-Realtime-2.1
Provider	OpenAI	OpenAI
Listed pricing route	OpenAI	OpenAI
Model family	gpt-nano	gpt
Accepted inputs	text, image	text, audio, image
Produced outputs	text	text, audio
Context window	400KHigher	128K
Max output	128KHigher	32K
Input price / 1M	$0.05Lower	$4.00
Output price / 1M	$0.40Lower	$24.00
Reasoning mode	Documented	Documented
Tool calling	Documented	Documented
Image input	Documented	Documented
Audio input	Not documented	Documented
Structured output	Documented	Not documented
License	Proprietary	Proprietary

GPT-5 Nano vs GPT-Realtime-2.1

GPT-5 Nano

GPT-Realtime-2.1

Key differences

Pricing, limits and capabilities

Which model should you choose?

Documentation and model profiles

Questions people ask

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