# GPT-5.5 Instant

> ChatGPT's fast default model from May 2026 to August 2026 — 52.5% fewer hallucinations on high-stakes prompts than GPT-5.3 Instant.

- Maker: OpenAI
- Line: GPT Instant
- Canonical page: https://ai-tldr.dev/models/gpt-5-5-instant/
- Updated: 2026-08-10

## In short

GPT-5.5 Instant is OpenAI's fast, low-latency model that became ChatGPT's default for all users on May 5, 2026, replacing GPT-5.3 Instant. It has a 1.05M-token context window and costs $5.00 per million input tokens and $30.00 per million output tokens. You can use it through OpenAI API.

## Facts

| Fact | Value | Source |
| --- | --- | --- |
| Context window | 1.05M (max output 128K) | [1] |
| Input price | $5.00 / 1M tokens (cached $0.50) | [2] |
| Output price | $30.00 / 1M tokens | [2] |
| Licence | Proprietary · API only | [1] |
| Released | 5 May 2026 | [3] |
| Parameters | Undisclosed | [1] |
| Knowledge cutoff | 1 December 2025 | [1] |

## Sources

1. [GPT-5.5 Instant System Card (OpenAI Deployment Safety Hub)](https://deploymentsafety.openai.com/gpt-5-5-instant)
2. [OpenAI API pricing](https://developers.openai.com/api/docs/pricing)
3. [GPT-5.5 Instant: smarter, clearer, and more personalized (OpenAI)](https://openai.com/index/gpt-5-5-instant/)

## Overview

GPT-5.5 Instant is OpenAI's fast, low-latency model that became ChatGPT's default for all users on May 5, 2026, replacing GPT-5.3 Instant. It was the everyday workhorse of the GPT Instant line — the model most people talked to in ChatGPT — tuned for quick, conversational replies without the extended deliberation of OpenAI's separate thinking models. OpenAI summarized the release as 'smarter, clearer, and more personalized.'

On August 6, 2026 OpenAI retired GPT-5.5 Instant from that role. Its GPT-5.6 August update states plainly that the newly released August versions of GPT-5.6 Sol and GPT-5.6 Luna 'will replace GPT-5.5 Instant': Free and Go users moved to GPT-5.6 Luna as the new everyday default, while Plus and Pro users moved to an updated GPT-5.6 Sol with a slider that controls how much effort ChatGPT spends on a response. OpenAI reported that both replacements cut factual error rates substantially versus GPT-5.5 Instant — roughly 60% across all three of its hallucination prompt sets for Sol, and over 60% on high-stakes prompts for Luna.

Compared with GPT-5.3 Instant, the headline improvement is factuality: OpenAI reported that GPT-5.5 Instant produces 52.5% fewer hallucinated claims on high-stakes prompts covering medicine, law, and finance, while keeping the same instant response latency. It also posts large jumps on hard reasoning and multimodal evaluations — 81.2 on AIME 2025 (up from 65.4) and 76 on the MMMU-Pro multimodal reasoning benchmark (up from 69.2).

GPT-5.5 Instant accepts text and image input and returns text. It adds deeper personalization: with memory enabled it can refer back to your past conversations, uploaded files, and (when connected) Gmail to give more tailored answers, and a new 'memory sources' view shows which stored context shaped each response so you can edit or remove individual entries. For developers, OpenAI exposes the model through the API as the chat-latest alias rather than a pinned snapshot, so apps on chat-latest track the current default. As a member of the GPT-5.5 family it carries the same 1,050,000-token context window, up to 128,000 output tokens, and a December 1, 2025 knowledge cutoff.

## Benchmarks

- AIME 2025 (math): 81.2% ([source](https://www.technobezz.com/news/openai-releases-gpt-55-instant-as-new-default-model-cutting-hallucinations-by-half))
- MMMU-Pro (multimodal reasoning): 76% ([source](https://www.technobezz.com/news/openai-releases-gpt-55-instant-as-new-default-model-cutting-hallucinations-by-half))
- Hallucination reduction vs GPT-5.3 Instant (high-stakes prompts): 52.5% ([source](https://www.technobezz.com/news/openai-releases-gpt-55-instant-as-new-default-model-cutting-hallucinations-by-half))
- HealthBench (length-adjusted): 51.4% ([source](https://deploymentsafety.openai.com/gpt-5-5-instant))
- HealthBench Hard (length-adjusted): 22.9% ([source](https://deploymentsafety.openai.com/gpt-5-5-instant))

## Pricing

- Input: $5.00 / 1M tokens
- Cached input: $0.50 / 1M tokens
- Output: $30.00 / 1M tokens

GPT-5.5 family rate; Instant is served via the chat-latest alias with no separate Instant tier.

Source: https://developers.openai.com/api/docs/pricing

## Strengths

- Much lower hallucination rate than GPT-5.3 Instant on high-stakes medical, legal, and financial prompts
- Instant, low-latency responses for everyday chat — no extended reasoning wait
- Strong multimodal reasoning over images and charts (MMMU-Pro 76)
- Built-in personalization from past conversations, files, and connected Gmail
- Very large 1,050,000-token context window for long documents and threads

## Best for

- Everyday ChatGPT conversation, drafting, and quick Q&A
- Higher-trust questions in medicine, law, and finance where factuality matters
- Image and chart understanding alongside text
- Personalized assistance grounded in your own history, files, and email
- Latency-sensitive chat apps that call the chat-latest API endpoint

## How to access

- [OpenAI API](https://developers.openai.com/api/docs/models/gpt-5.5) — model id `chat-latest`

## GPT Instant versions

- GPT-5.5 Instant (5 May 2026): ChatGPT default from May 5, 2026 until the August 6, 2026 GPT-5.6 update; 52.5% fewer hallucinations on high-stakes prompts than GPT-5.3 Instant — this page
- [GPT-5.3 Instant](https://ai-tldr.dev/models/gpt-5-3-instant/) (3 March 2026)
- [GPT-5.2 Instant](https://ai-tldr.dev/models/gpt-5-2-instant/) (11 December 2025)
- [GPT-5.1 Instant](https://ai-tldr.dev/models/gpt-5-1-instant/) (12 November 2025)

## FAQ

### What is GPT-5.5 Instant and how is it different from GPT-5.5?

GPT-5.5 Instant is the fast, low-latency model in OpenAI's GPT Instant line that became ChatGPT's default for all users on May 5, 2026. It answers quickly without the extended deliberation of OpenAI's separate thinking models. It is part of the same GPT-5.5 family as the flagship GPT-5.5 (announced April 23, 2026) and shares its 1,050,000-token context window and December 1, 2025 knowledge cutoff, but it is tuned for speed and everyday conversation rather than long reasoning.

### How much more accurate is GPT-5.5 Instant than GPT-5.3 Instant?

OpenAI reported that GPT-5.5 Instant produces 52.5% fewer hallucinated claims than GPT-5.3 Instant on high-stakes prompts covering medicine, law, and finance. It also improved on hard benchmarks, scoring 81.2 on AIME 2025 (up from 65.4) and 76 on MMMU-Pro multimodal reasoning (up from 69.2).

### How do I use GPT-5.5 Instant through the API?

OpenAI serves GPT-5.5 Instant through the API as the chat-latest alias rather than a pinned snapshot, so requests to chat-latest track ChatGPT's current default model. As a GPT-5.5 family model it is priced at $5.00 per 1M input tokens and $30.00 per 1M output tokens, with cached input at $0.50 per 1M tokens; there is no separate Instant pricing tier.

### Is GPT-5.5 Instant still ChatGPT's default model?

No. On August 6, 2026 OpenAI replaced GPT-5.5 Instant in ChatGPT: Free and Go users were moved to the August release of GPT-5.6 Luna as the new everyday default, and Plus and Pro users were moved to an updated GPT-5.6 Sol with an effort slider. Between May 5, 2026 and that date GPT-5.5 Instant was the default for all users, including the free tier, with personalization features rolling out first to Plus and Pro on the web.

## Links

- [GPT-5.5 Instant: smarter, clearer, and more personalized (OpenAI)](https://openai.com/index/gpt-5-5-instant/)
- [GPT-5.5 Instant System Card (OpenAI Deployment Safety Hub)](https://deploymentsafety.openai.com/gpt-5-5-instant)
- [GPT-5.6 — August Updates (OpenAI Deployment Safety Hub, August 6, 2026) — the release that replaced GPT-5.5 Instant](https://deploymentsafety.openai.com/gpt-5-6-august-update)
- [GPT-5.5 model docs (OpenAI API)](https://developers.openai.com/api/docs/models/gpt-5.5)
- [OpenAI API pricing](https://developers.openai.com/api/docs/pricing)
- [OpenAI releases GPT-5.5 Instant, a new default model for ChatGPT (TechCrunch)](https://techcrunch.com/2026/05/05/openai-releases-gpt-5-5-instant-a-new-default-model-for-chatgpt/)
- [GPT-5.5 Instant benchmarks and details (Technobezz)](https://www.technobezz.com/news/openai-releases-gpt-55-instant-as-new-default-model-cutting-hallucinations-by-half)
- [GPT-5.5 (Wikipedia)](https://en.wikipedia.org/wiki/GPT-5.5)
- [Try GPT-5.5 Instant in ChatGPT](https://chatgpt.com)

Source: AI/TLDR LLM registry, https://ai-tldr.dev/models/gpt-5-5-instant/