The GPT-4-series is 📝OpenAI's fourth generation of 📝GPT models, spanning GPT-4 (March 2023) through GPT-4o, GPT-4.5, and GPT-4.1 (2025), which powered 📝ChatGPT until the arrival of GPT-5.

The series took OpenAI from text-only models to fully multimodal ones. GPT-4 added image input, GPT-4 Turbo stretched the context window to 128,000 tokens, and GPT-4o unified text, audio, and image input and output in a single network. Later releases split in two directions: GPT-4.5 was a very large research preview, while the GPT-4.1 family offered developers a 1M-token context window through the API. 📝GPT-5 replaced the series as ChatGPT's default in August 2025, and OpenAI retired the remaining GPT-4-series models from ChatGPT on February 13, 2026.

Key Facts

Developer: OpenAI
Span: March 14, 2023 (GPT-4) to April 14, 2025 (GPT-4.1)
Successor: GPT-5, released August 7, 2025
ChatGPT retirement: GPT-4 on April 30, 2025; GPT-4o, GPT-4.1, and GPT-4.1 mini on February 13, 2026
API shutdown: GPT-4, GPT-4 Turbo, the original GPT-4o snapshot, and GPT-4.1 nano on October 23, 2026

Models in the Series

GPT-4 — released March 14, 2023: OpenAI's first multimodal flagship, accepting text and image input, with 8K- and 32K-token versions.
GPT-4 Turbo — released November 6, 2023: a faster, cheaper GPT-4 with a 128K-token context window.
GPT-4o — released May 13, 2024: the "omni" model handling text, audio, and images in one network; its native image generation arrived in ChatGPT on March 25, 2025.
GPT-4o mini — released July 18, 2024: the low-cost version of GPT-4o.
GPT-4.5 — released February 27, 2025: a large research-preview model, retired from the API on July 14, 2025.
GPT-4.1, GPT-4.1 mini, and GPT-4.1 nano — released April 14, 2025: API-first models that introduced a 1M-token context window.

Why It Matters

GPT-4 set the benchmark that the 📝rest of the industry chased through 2023 and 2024, and GPT-4o made real-time voice and vision mainstream in ChatGPT. The series also showed how attached users become to a model's personality: when GPT-5 first replaced GPT-4o in August 2025, OpenAI restored GPT-4o after user backlash, and its final retirement in February 2026 drew renewed criticism even though OpenAI reported that only about 0.1% of users still chose it daily.

FAQ

Is GPT-4 still available?

Not in ChatGPT, which retired its last GPT-4-series models on February 13, 2026. Several GPT-4-series models remain in the OpenAI API until their scheduled shutdown on October 23, 2026.

What is the difference between GPT-4 and GPT-4o?

GPT-4 accepted text and images and returned text. GPT-4o is a single "omni" model that handles text, audio, and images as both input and output, which made it faster and enabled real-time voice conversations.

What replaced the GPT-4-series?

GPT-5, released August 7, 2025, replaced it as ChatGPT's default. OpenAI's deprecation notices point API developers to GPT-5.6 Sol, Terra, or Luna.

📝OpenAI Model Glossary — every OpenAI model by family
📝GPT-3 — the generation before GPT-4