Not many people think about the under-the-hood models powering ChatGPT. To the average user, the incremental updates to the world’s fastest growing product have just meant that sometimes it feels like its getting smarter (or that now a brief Thinking… dialogue appears when a hard question is asked). More technical users pay closer attention, tracking each and every little change that each of OpenAI’s nine model releases have brought to the platform.
Today’s update isn’t a little change; this is the big one. GPT-5, worthy of the full number upgrade, promises to wow ChatGPT users in a way that hasn’t happened since GPT-4’s release in 2023.
TL;DR
- GPT-5 will be the default ChatGPT model for all users (including folks on the Free plan!)
- Strongest model on coding, reasoning, tool use, and agentic benchmarks
- 400k token context window (128k output max)
- Comes in three sizes (full, mini, nano); all available via API
- Safer, less hallucinatory (reduced by ~80%), better instruction-following
- New dev controls:
reasoning_effort,verbosity, and plaintext custom tools - System-level router picks the right sub-model (fast vs. deep reasoning) per query
- Miscellanous ChatGPT product updatesChange the colors of ChatGPT
- New “personalities” feature preview coming
- Gmail and Google Calendar access
The fine details
GPT-5 keeps OpenAI’s promise of combining all its model variations into a single system.
In ChatGPT, you’ll be talking to a multi-model router that evaluates what type of request you’re making and dynamically delegates between “thinking” (high-reasoning) and “main” (fast-response) models. That router learns in real time for each user, incorporating model-switch patterns, preference signals, and correctness outcomes. (For example, you can say “think hard about this” in your prompt and watch it change behavior.)
GPT-5 will now powering ChatGPT by default, even for free-tier users. The fast-response model (gpt-5-main) handles most queries, and the smarter model (gpt-5-thinking) gets routed in for hard ones.