Reasoning · OpenAI
Run gpt-oss-20b in the EU through an OpenAI-compatible API
gpt-oss-20b is the smaller of OpenAI's two open-weight reasoning models: 21 billion parameters, 3.6 billion active per token, released under Apache 2.0. On inference.eu you call it with the OpenAI SDK you already use, while your prompts are processed in EU data centres and never used for training.
- 0121B · 3.6B
- 02EU data centres
- 03Apache 2.0
What gpt-oss-20b is
gpt-oss-20b was released by OpenAI in August 2025 together with gpt-oss-120b. It is a mixture-of-experts model with 21 billion parameters, of which 3.6 billion are active for each token, and a 128K-token context window. Its expert weights were post-trained in MXFP4 precision, so the model fits within 16 GB of memory.
Like its larger sibling, it reasons before answering, and you set the reasoning effort per request to low, medium or high. It was trained on OpenAI's harmony response format and supports function calling and structured outputs natively. It reads and writes text only. OpenAI positions it for lower-latency and specialised use cases.
What it does well, and where it falls short
gpt-oss-20b is a quick, inexpensive reasoning model for everyday tasks: answering support questions, extracting fields into JSON, routing requests to tools and handling short analytical questions. With only 3.6 billion active parameters it responds fast, and the adjustable reasoning effort lets you spend thinking only where a request needs it.
It is clearly weaker than gpt-oss-120b on hard maths, long code changes and broad world knowledge, and its knowledge is older than 2026 models. It has no image or audio input. OpenAI does not publish a list of supported languages, so check quality in German, French or other European languages against your own content first.
Calling gpt-oss-20b through the API
If your code uses the OpenAI SDK, change the base URL to the inference.eu API, use your inference.eu key and set the model to gpt-oss-20b. The harmony format is handled on our side, so you send and receive ordinary chat messages.
Pass reasoning_effort as low for fast replies or high for careful answers. Function calling, JSON schema outputs and streaming work as in OpenAI's own API. The chain of thought is intended for debugging, not for end users, so show only the final answer in your interface. The Anthropic Messages format is also available if your tools were built for Claude.
Data residency for gpt-oss-20b
On inference.eu the open weights of gpt-oss-20b run on infrastructure in the European Union. Prompts and responses are processed in EU data centres, nothing is sent to OpenAI, and nothing is used to train any model. That is the main difference from calling OpenAI's hosted models.
Every customer receives a data processing agreement under Article 28 of the GDPR and our list of subprocessors, so your records of processing can name every party involved. Billing is in euros. The Apache 2.0 licence permits commercial use without user limits; OpenAI adds a short usage policy that asks you to comply with applicable law.
import os
from openai import OpenAI
client = OpenAI(base_url="https://api.inference.eu/v1", api_key=os.environ["INFERENCE_EU_API_KEY"])
response = client.chat.completions.create(
model="gpt-oss-20b",
messages=[{"role": "user", "content": "Summarise this contract in five bullet points."}],
)
print(response.choices[0].message.content)What teams use it for
- 1
Fast support answers
Answer routine customer questions with a short reasoning step, at a size that keeps response times low.
- 2
Tool routing
Decide which internal API or workflow should handle a request and fill in the parameters as structured JSON.
- 3
Data extraction with checks
Pull fields from emails and documents and reason briefly about whether the values are consistent.
gpt-oss-20b: common questions
The questions buyers, developers and legal teams ask us most. Something missing? Ask us directly.
Related
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