Sharing the latest Model Spec

Introducing the Model Spec

OpenAI GPT-4.5 System Card

We’re releasing a research preview of OpenAI GPT‑4. 5, our largest and most knowledgeable model yet.

Introducing improvements to the fine-tuning API and expanding our custom models program

We’re adding new features to help developers have more control over fine-tuning and announcing new ways to build custom models with OpenAI.

Introducing OpenAI o3 and o4-mini

Our smartest and most capable models to date with full tool access

gpt-oss-120b & gpt-oss-20b Model Card

We introduce gpt-oss-120b and gpt-oss-20b, two open-weight reasoning models available under the Apache 2. 0 license and our gpt-oss usage policy.

GPT-2: 1.5B release

As the final model release of GPT-2’s staged release, we’re releasing the largest version (1. 5B parameters) of GPT-2 along with code and model weights to facilitate detection of outputs of GPT-2 models.