GPT OSS 20B API

OpenAI’s GPT OSS 20B offers flexible reasoning levels, agentic features, and robust coding support in an open-source, memory-efficient transformer.

Modalities: TextText
In / Out price: $0.05/$0.2per 1M
Context window: 131K tokens
Released: Sep 9, 2025

GPT OSS 20B overview

GPT OSS 20B by OpenAI

Lightweight yet powerful, GPT OSS 20B supports multi-step workflows, tool integration, and runs efficiently on hardware with 16GB memory.

GPT OSS 20B specs

Model ID: openai/gpt-oss-20b
Developer: OpenAI
Context window: 131,000 tokens
Max output: 117,964 tokens
Input: Text
Output: Text
API: OpenAI-compatible, base URL https://api.aimlapi.com/v1

GPT OSS 20B is an open-weight language model by OpenAI optimized for efficient, local, and specialized use cases with strong reasoning and coding capabilities. It offers a balance of high performance and low latency, making it suitable for edge devices and applications needing rapid iteration or lower compute requirements. Designed for agentic workflows, it supports chain-of-thought reasoning, function calling, and Python code execution, with customizable reasoning effort and structured output capabilities.

Technical Specifications

Model Size: 20 billion parameters with 3.6 billion active parameters
Compatibility: Runs within 16GB memory, optimized for lower latency and local deployment
Architecture: Text-only model supporting strong instruction following and tool usage

Performance Benchmarks

Demonstrates performance comparable to OpenAI’s proprietary o3-mini model on many reasoning and coding tasks
Efficient for deployment on consumer-grade hardware and edge devices
Strong in few-shot learning, multi-step reasoning, and tool integration

Key Capabilities

Advanced Reasoning: Configurable reasoning effort levels (low, medium, high) to balance accuracy and latency
Agentic Features: Supports function calling, web browsing, code execution, and structured outputs within workflows
Code Generation: Produces and edits code effectively across multiple programming languages
Lightweight Deployment: Runs efficiently in constrained environments with modest hardware requirements

Optimal Use Cases

On-device AI applications requiring lightweight but capable models
Rapid experimentation and iterations in coding and analytic tasks
Applications benefitting from flexible reasoning depth and tool integration
Local or offline deployments demanding privacy and data control

Comparison with Other Models

vs GPT OSS 120B: GPT OSS 20B operates efficiently on limited hardware with 16GB memory, making it well-suited for local and rapid deployment with solid reasoning and coding capabilities, whereas GPT OSS 120B offers significantly larger capacity (120B parameters), delivers higher accuracy, and is designed for large-scale, high-compute tasks.

vs OpenAI o3-mini: GPT OSS 20B demonstrates comparable performance to the o3-mini model, with the added advantage of open-weight access and flexible configuration, benefiting researchers and developers who require transparency and customization.

vs GLM-4.5: GLM-4.5 outperforms GPT OSS 20B in practical coding challenges and advanced tool integration, but GPT OSS 20B remains competitive in general reasoning tasks and is easier to deploy on hardware with limited resources.

Limitations and Considerations

While more affordable than larger models, it is less powerful than GPT OSS 120B for extremely complex tasks
Best used with explicit prompt design to achieve optimal outputs
Performance and latency depend on hardware capabilities and input size
Open-weight nature means enterprises should apply additional safeguards for production safety

Use cases

On-device AI applications requiring lightweight but capable models
Rapid experimentation and iterations in coding and analytic tasks
Applications benefitting from flexible reasoning depth and tool integration
Local or offline deployments demanding privacy and data control

Capabilities

Function calling
Streaming
Structured outputs
Reasoning
Web search

GPT OSS 20B benchmarks by Artificial Analysis

See how GPT OSS 20B compares in generation speed and latency. Data retrieved Nov 4, 2026.

Speed#65 / 219150Output tokens / second Latency#14 / 2160.71Seconds to first token Humanity's Last Exam#201 / 45811%Score GPQA Diamond#226 / 43968.8%Score

Speed

Output tokens / second

Benchmark results

Compare 9 models available on AI/ML API across 5 independent benchmarks.

Humanity's Last Exam

Expert-written questions across academic subjects.

GPT OSS 20B API pricing

GPT OSS 20B pricing in US dollars
Usage	Price	Unit
Input	$0.05	1M tokens
Output	$0.2	1M tokens
Cached input	$0.0397	1M tokens

Prices from the AI/ML API price list, checked on Nov 4, 2026.

GPT OSS 20B vs other models: token prices

AI/ML API input and output rates for 5 models, per million tokens.

AI/ML API model prices in USD per million tokens
Model	Input	Output
GPT OSS 20B	$0.05	$0.2
GPT-6.1 Terra	$1	$5
GPT-6.1 Sol	$2	$10
GPT-6 Sol	$2	$10
GPT-6.1 Terra Pro	$2.12	$10.58

How to use the GPT OSS 20B API

View docs

Build with your agent

Give your agent the model details, code and documentation.

1Get your API key

Create API key

export AIMLAPI_KEY="8f2b4c7d9a1e6b3f…"

2Make your first request

curl 'https://api.aimlapi.com/v1/chat/completions' \
  -H "Authorization: Bearer $AIMLAPI_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
  "model": "openai/gpt-oss-20b",
  "messages": [
    {
      "role": "user",
      "content": "Write a haiku about the ocean."
    }
  ]
}'

import os
import requests

headers = {
    "Authorization": f"Bearer {os.environ['AIMLAPI_KEY']}",
    "Content-Type": "application/json",
}
payload = {
    "model": "openai/gpt-oss-20b",
    "messages": [
        {
            "role": "user",
            "content": "Write a haiku about the ocean."
        }
    ]
}

response = requests.post("https://api.aimlapi.com/v1/chat/completions", headers=headers, json=payload, timeout=120)
response.raise_for_status()
print(response.json())

const response = await fetch("https://api.aimlapi.com/v1/chat/completions", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.AIMLAPI_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "model": "openai/gpt-oss-20b",
    "messages": [
      {
        "role": "user",
        "content": "Write a haiku about the ocean."
      }
    ]
  }),
});

if (!response.ok) throw new Error(`HTTP ${response.status}`);
console.log(await response.json());

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GPT OSS 20B FAQ

What is the context window of GPT OSS 20B?

GPT OSS 20B has a 131,000 tokens context window and can return up to 131,072 tokens.

What inputs and outputs does GPT OSS 20B support?

GPT OSS 20B takes text as input and returns text.

What is the model ID for GPT OSS 20B?

Use openai/gpt-oss-20b as the model id. Requests go to https://api.aimlapi.com/v1/chat/completions.

When was GPT OSS 20B released?

GPT OSS 20B became available on September 9, 2025.

How much does GPT OSS 20B cost?

GPT OSS 20B costs $0.05 input and $0.2 output per 1M tokens on AI/ML API, billed as you go with no subscription.

Does GPT OSS 20B support streaming?

Yes, GPT OSS 20B can stream responses as they are generated.

Who created GPT OSS 20B?

GPT OSS 20B was built by OpenAI.

Start building with GPT OSS 20B

Get API key

GPT OSS 20B API

openai/gpt-oss-20b

Build with your agent

Give your agent the model details, code and documentation.

1Get your API key

Create API key

export AIMLAPI_KEY="8f2b4c7d9a1e6b3f…"

2Make your first request

curl 'https://api.aimlapi.com/v1/chat/completions' \
  -H "Authorization: Bearer $AIMLAPI_KEY" \
  -H 'Content-Type: application/json' \
  -d '{
  "model": "openai/gpt-oss-20b",
  "messages": [
    {
      "role": "user",
      "content": "Write a haiku about the ocean."
    }
  ]
}'

import os
import requests

headers = {
    "Authorization": f"Bearer {os.environ['AIMLAPI_KEY']}",
    "Content-Type": "application/json",
}
payload = {
    "model": "openai/gpt-oss-20b",
    "messages": [
        {
            "role": "user",
            "content": "Write a haiku about the ocean."
        }
    ]
}

response = requests.post("https://api.aimlapi.com/v1/chat/completions", headers=headers, json=payload, timeout=120)
response.raise_for_status()
print(response.json())

const response = await fetch("https://api.aimlapi.com/v1/chat/completions", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${process.env.AIMLAPI_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "model": "openai/gpt-oss-20b",
    "messages": [
      {
        "role": "user",
        "content": "Write a haiku about the ocean."
      }
    ]
  }),
});

if (!response.ok) throw new Error(`HTTP ${response.status}`);
console.log(await response.json());

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GPT OSS 20B API

GPT OSS 20B overview

GPT OSS 20B by OpenAI

GPT OSS 20B specs

Technical Specifications

Performance Benchmarks

Key Capabilities

Optimal Use Cases

Comparison with Other Models

Limitations and Considerations

Use cases

Capabilities

GPT OSS 20B benchmarks by Artificial Analysis

Speed

Benchmark results

Humanity's Last Exam

GPQA Diamond

Terminal-Bench 4.0

AA-LCR

SciCode

GPT OSS 20B API pricing

GPT OSS 20B vs other models: token prices

How to use the GPT OSS 20B API

Build with your agent

1Get your API key

2Make your first request

Related articles

GPT OSS 20B FAQ

Start building with GPT OSS 20B

GPT OSS 20B API

Build with your agent

1Get your API key

2Make your first request

GPT OSS 20B API

GPT OSS 20B overview

GPT OSS 20B by OpenAI

GPT OSS 20B specs

Technical Specifications

Performance Benchmarks

Key Capabilities

Optimal Use Cases

Comparison with Other Models

Limitations and Considerations

Use cases

Capabilities

Speed

Benchmark results

Humanity's Last Exam

GPQA Diamond

Terminal-Bench 4.0

AA-LCR

SciCode

GPT OSS 20B API pricing

GPT OSS 20B vs other models: token prices

How to use the GPT OSS 20B API

Build with your agent

1Get your API key

2Make your first request

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