ChatGPT Models Guide: Unlocking the Power of GPT-5.6, GPT-5.5 and More

OpenAI offers GPT-5.6 Sol, GPT-5.6 Terra, GPT-5.6 Luna, GPT-5.5, GPT-5.5 Pro, GPT-5.4, GPT-5.4 Pro, GPT-5.4 mini, GPT-5.4 nano in 2026. Older models (GPT-4o, o3, o4-mini, and earlier) were retired on February 13, 2026 and replaced by the GPT-5.x family. Free users get a default everyday model, while Plus and Pro subscribers access the full lineup, led by the GPT-5.6 Sol frontier model and including the GPT-5.5 Pro and GPT-5.4 Pro reasoning-grade variants.

The best ChatGPT model depends on your task. GPT-5.6 Sol is OpenAI's flagship frontier model for complex professional work, GPT-5.6 Terra balances intelligence and cost, and GPT-5.6 Luna is tuned for cost-sensitive, high-volume workloads. In the earlier generations, GPT-5.5 Pro and GPT-5.4 Pro handle the most demanding reasoning, GPT-5.5 and GPT-5.4 balance speed and intelligence, and GPT-5.4 mini and GPT-5.4 nano are ideal for quick everyday tasks. AI Toolbox (35,000+ users) works with all models and helps you organize conversations by model type using folders.

GPT-5.6 is OpenAI's newest frontier family, launched July 2026. GPT-5.6 Sol is the flagship for complex professional work, GPT-5.6 Terra balances intelligence and cost, and GPT-5.6 Luna is optimized for cost-sensitive, high-volume tasks. All three share a roughly 1M-token context window and add a new max reasoning effort plus an ultra mode that leverages subagents for complex work. They sit above the GPT-5.5 and GPT-5.4 generations, which remain available.