GPT (Generative Pre-trained Transformer) is 📝OpenAI's family of 📝Large Language Model (LLM) systems, from GPT-1 in 2018 to the GPT-6 family in September 2026, and the technology behind 📝ChatGPT.
Each GPT model is a transformer network pre-trained to predict the next token across enormous amounts of text, then refined with human feedback and other post-training so it follows instructions and uses tools. The line has grown from a research demonstration into OpenAI's commercial core: it powers ChatGPT, the 📝Codex coding agent, and the OpenAI API. The term "GPT" is also used loosely for chatbots in general, and OpenAI uses "GPTs" for the 📝Custom GPTs users build inside ChatGPT.
Key Facts
- Developer: OpenAI
- First model: GPT-1, June 11, 2018
- Current flagship: GPT-6 Astra, released September 3, 2026
- Architecture: decoder-only transformer, pre-trained on next-token prediction
- Naming: since GPT-5.6 (July 2026), OpenAI names capability tiers — Sol, Terra, and Luna, then Astra, Sol, and Luna for GPT-6
- Status as of: September 28, 2026
Lineage
- GPT-1 and GPT-2 (2018–2019) — proved that unsupervised pre-training transfers to many tasks; GPT-2 was released in stages over misuse concerns.
- 📝GPT-3 (2020) — scaled to 175 billion parameters and launched OpenAI's commercial API.
- GPT-3.5 (2022) — instruction-tuned descendants that became the model behind ChatGPT's November 2022 launch.
- 📝GPT-4-series (2023–2025) — added image input, then native multimodality with GPT-4o and 1M-token context with GPT-4.1.
- 📝GPT-5 (2025–2026) — unified fast and reasoning models behind a router, iterating through 📝GPT-5.5 to the tiered GPT-5.6 family.
- GPT-6 (2026) — GPT-6 Astra, Sol, and Luna, OpenAI's current generation.
FAQ
What does GPT stand for?
GPT stands for Generative Pre-trained Transformer: a model that generates text, is pre-trained on large datasets, and uses the transformer neural-network architecture.
What is the latest GPT model?
As of September 28, 2026, the latest is the GPT-6 family: GPT-6 Astra (September 3, 2026) and GPT-6 Sol and Luna (September 22, 2026).
Is GPT the same as ChatGPT?
No. GPT is the family of models; ChatGPT is OpenAI's chat product that runs on them.
Related
- 📝OpenAI Model Glossary — every GPT, o-series, image, video, and voice model with dates