GPT-5.1 Chat

Retired

OpenAI · November 2025

OpenAI retired this model on 23 July 2026, so you can't start new chats with it. Your previous conversations are still available.

The build that ran ChatGPT for GPT-5.1. Tuned for conversation, with a short thinking step.

Best for: Everyday chat
Superseded by: GPT-5.2 Chat

Context window
128,000 tokens
≈ 96,000 words · about 380 pages
Max output
16,384 tokens
≈ 12,000 words in a single answer
Knowledge cutoff
September 2024
its training cutoff

Modalities

TextInput and output
ImageInput only
AudioNot supported
VideoNot supported

Reasoning effort

Low
Medium
High

Features

StreamingSupported
Function callingSupported
Structured outputsSupported
Fine-tuningNot supported

Ready to try it?

Polymeti is currently invite-only.

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Bring your own API key · Your chats stay in your browser