Speed
Output tokens / second
GPT OSS 120B overview
GPT OSS 120B by OpenAI
GPT OSS 120B is a large-scale open-source language model with 120 billion parameters, designed for advanced reasoning, code generation, and extended context processing.
GPT OSS 120B specs
- Model ID
openai/gpt-oss-120b- 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 120B is a large-scale open-source language model designed for high-capacity reasoning, coding, and general-purpose tasks. It balances state-of-the-art performance typical of 100+ billion parameter models with relative cost efficiency, enabling broad accessibility for researchers and developers. GPT OSS 120B excels across text generation, multi-step logical reasoning, and multilingual understanding, supporting both general and specialized applications.
Technical Specifications
- Strong performance in reasoning benchmarks with accuracy near top-tier GPT models
- Excels in academic and industry coding challenges, competing with other large foundation models
- Robust multi-domain reasoning, including STEM-focused tasks, natural language understanding, and complex dialogue
Performance Benchmarks
- Model Size: 120 billion parameters
Optimal Use Cases
- Large-scale document analysis and synthesis
- Complex software development and debugging assistance
- Research requiring deep reasoning and multi-step workflows
- Multimodal AI applications involving textual and visual data
- Cost-aware deployment for applications needing high model capacity
Comparison with Other Models
vs GPT-4o Mini: GPT OSS 120B offers a much larger parameter count and excels in high-capacity reasoning and code generation, while GPT-4o Mini is smaller and more cost-efficient, with built-in multimodal support for both text and images.
vs GLM-4.5: Although GLM-4.5 has more total and active parameters and leads in advanced tool integration and agentic task performance, GPT OSS 120B remains competitive with strong reasoning benchmarks and greater efficiency on smaller hardware.
Limitations and Considerations
- Higher cost compared to smaller models, reflecting advanced capabilities and scale
- Requires explicit prompt design for optimal performance in highly creative or open-ended tasks
- Latency and throughput depend on input size and model load, with larger contexts incurring longer processing times
Use cases
- Large-scale document analysis and synthesis
- Complex software development and debugging assistance
- Research requiring deep reasoning and multi-step workflows
- Multimodal AI applications involving textual and visual data
- Cost-aware deployment for applications needing high model capacity
Capabilities
- Function calling
- Streaming
- Structured outputs
- Reasoning
- Web search
GPT OSS 120B benchmarks by 
Artificial Analysis
See how GPT OSS 120B compares in generation speed and latency. Data retrieved Nov 4, 2026.
Benchmark results
Compare 9 models available on AI/ML API across 5 independent benchmarks.
Humanity's Last Exam
Expert-written questions across academic subjects.
GPQA Diamond
Graduate-level science questions written to resist web search.
Terminal-Bench 4.0
Agentic tasks completed in a command-line environment.
AA-LCR
Reasoning across long documents of about 100k tokens.
SciCode
Python coding tasks drawn from scientific research.
GPT OSS 120B API pricing
| Usage | Price | Unit |
|---|---|---|
| Input | $0.15 | 1M tokens |
| Output | $0.6 | 1M tokens |
| Cached input | $0.3703 | 1M tokens |
Prices from the AI/ML API price list, checked on Nov 4, 2026.
GPT OSS 120B vs other models: token prices
AI/ML API input and output rates for 5 models, per million tokens.
| Model | Input | Output |
|---|---|---|
 GPT OSS 120B | $0.15 | $0.6 |
| 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 120B API
View docs
Build with your agent
Give your agent the model details, code and documentation.
Paste it into your coding agent to build the integration.
1Get your API key
Create API keyexport 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-120b",
"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-120b",
"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-120b",
"messages": [
{
"role": "user",
"content": "Write a haiku about the ocean."
}
]
}),
});
if (!response.ok) throw new Error(`HTTP ${response.status}`);
console.log(await response.json());Models similar to GPT OSS 120B
Related articles
GPT OSS 120B FAQ
What is the context window of GPT OSS 120B?
GPT OSS 120B has a 131,000 tokens context window and can return up to 131,072 tokens.
What inputs and outputs does GPT OSS 120B support?
GPT OSS 120B takes text as input and returns text.
What is the model ID for GPT OSS 120B?
Use openai/gpt-oss-120b as the model id. Requests go to https://api.aimlapi.com/v1/chat/completions.
When was GPT OSS 120B released?
GPT OSS 120B became available on September 9, 2025.
How much does GPT OSS 120B cost?
GPT OSS 120B costs $0.15 input and $0.6 output per 1M tokens on AI/ML API, billed as you go with no subscription.
Does GPT OSS 120B support streaming?
Yes, GPT OSS 120B can stream responses as they are generated.
Who created GPT OSS 120B?
GPT OSS 120B was built by OpenAI.
Can I access GPT OSS 120B through OpenAI's own API?
It is accessed via the endpoint https://api.aimlapi.com/v1/chat/completions, not directly through OpenAI's own API.