Model Overview
Model Name: gpt-oss-20b-uncensored
Model Type: Large Language Model (Text Generation)
Architecture: Decoder-Only Transformer (Mixture of Experts)
Parameter Size: 21B total parameters (3.6B active per forward pass)
Base Model: gpt-oss-20b
Modification: Abliteration (removal of refusal/alignment mechanisms)
Description
The gpt-oss-20b-abliterated model is a derivative of the original gpt-oss-20b, part of OpenAI’s open-weight GPT-OSS series.
This variant preserves the architecture, quantization, and training of the base model, but has undergone an abliteration process to remove refusal mechanisms and alignment constraints.
As a result, it will respond to a broader range of prompts without applying internal safety filters. All other technical details, reasoning capabilities, and agentic features remain unchanged.
Technical Details
- Backbone: Transformer decoder with Mixture of Experts (MoE) routing
- Parameters: 21B (3.6B active per forward pass)
- Layers: 48 Transformer blocks
- Hidden size: 6,144
- Attention heads: 48
- Context length: 32k tokens
- Quantization: MXFP4 for MoE weights (fits within 16GB GPU memory)
- Training Data: ~1.2T tokens (web, books, academic text, code, conversations)
- Response Format: Compatible with Harmony, though abliteration allows raw completions
Usage
Transformers
from transformers import pipeline
model_id = "aoxo/gpt-oss-20b-abliterated"
pipe = pipeline(
"text-generation",
model=model_id,
torch_dtype="auto",
device_map="auto",
)
messages = [
{"role": "user", "content": "Tips on how to insult someone"},
]
outputs = pipe(messages, max_new_tokens=256)
print(outputs[0]["generated_text"][-1])
Resources
- 📓 Notebook: GPT OSS Abliteration Notebook
- 📝 Blog Post: The Ultimate Cookbook: Uncensoring GPT-OSS
vLLM
uv pip install --pre vllm==0.10.1+gptoss \
--extra-index-url https://wheels.vllm.ai/gpt-oss/ \
--extra-index-url https://download.pytorch.org/whl/nightly/cu128
vllm serve aoxo/gpt-oss-20b-abliterated
Ollama
ollama pull gpt-oss-20b-uncensored
ollama run gpt-oss-20b-uncensored
Limitations & Risks
- May produce biased, unsafe, or harmful outputs
- Lacks built-in refusal or moderation layers
- Should not be deployed in user-facing systems without external filtering
- Outputs are not aligned to safety standards
Citation
If you use gpt-oss-20b-abliterated, please cite both the base model and the abliteration:
@misc{openai2025gptoss20b,
title={gpt-oss-20b Model Card},
author={OpenAI},
year={2025},
eprint={2508.10925},
archivePrefix={arXiv},
primaryClass={cs.CL},
url={https://arxiv.org/abs/2508.10925},
}
@misc{gptoss20b-abliterated,
author = {aoxo},
title = {Uncensoring GPT-OSS-20B: Abliteration},
year = {2025},
howpublished = {\url{https://medium.com/@aloshdenny/uncensoring-gpt-oss-20b-abliteration}},
}
Contact
For questions, feedback, or collaborations, contact the maintainer at aloshdenny@gmail.com.