GPT-5.1 Instant

// Overview

GPT-5.1 Instant is OpenAI's fast, high-throughput default ChatGPT model, released on November 12, 2025 (and on the API platform November 13). It is the low-latency, non-extended-reasoning member of the GPT-5.1 family — the sibling of GPT-5.1 Thinking — and is exposed to developers through the gpt-5.1-chat-latest snapshot, the same model that powers the default Instant mode in ChatGPT.

The headline change in GPT-5.1 Instant is adaptive reasoning: for the first time, the Instant model can decide when to briefly "think" before responding to a harder question, catching nuances and constraints that earlier chat models glossed over, while still answering simple prompts quickly. OpenAI also positions it as warmer, more conversational, and better at following instructions than previous default models, with new tone and personality presets (such as Professional, Candid, and Quirky) and controls over conciseness, warmth, and emoji use.

On specs, GPT-5.1 Instant accepts text and image input and returns text, with a 128,000-token context window and up to 16,384 output tokens, and a knowledge cutoff of September 30, 2024. It is priced at $1.25 per million input tokens (with cached input at $0.125) and $10 per million output tokens. OpenAI recommends the Instant/chat snapshot for testing the latest ChatGPT chat behavior, while pointing developers toward the full GPT-5.1 reasoning model (400K context) for heavier agentic and coding workloads.

// Pricing

Pricing for the gpt-5.1-chat-latest snapshot (GPT-5.1 Instant). Cached input is discounted 90%.

Pricing source ↗

// Strengths

• Low latency and high throughput as OpenAI's default everyday ChatGPT model
• New adaptive reasoning — decides when to think before answering harder questions while staying fast on simple ones
• Warmer, more conversational tone with stronger instruction following
• Customizable personality and tone presets (Professional, Candid, Quirky, Friendly, and more) plus conciseness/warmth/emoji controls
• Text and image (vision) input
• Same snapshot as ChatGPT's default, so API behavior mirrors the consumer product

// Best for

• Everyday conversational assistant and default ChatGPT experience
• High-volume chat and customer-facing assistants where latency and cost matter
• Quick drafting, rewriting, summarizing, and Q&A
• Image understanding and visual question answering via vision input
• Prototyping and testing the latest ChatGPT chat behavior in the API
• Lightweight tool use across math, coding, and multi-step tasks without full extended reasoning

// How to access

// GPT Instant — every version

The full lineage of the GPT Instant line, newest first. Every version has its own page — click any to compare specs, benchmarks and pricing.