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ChatGPT Upgrades to GPT-5.5 Instant in May 2026 to Reduce Hallucinations

OpenAI has begun rolling out GPT-5.5 Instant as the new default model for all ChatGPT users. The update focuses on improving factual accuracy, with the company claiming a significant reduction in 'hallucinated' claims, particularly in high-stakes fields like medicine and law.

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  1. A New Default Model
  2. Targeting Factuality
  3. A Push for Transparency
  4. Refinement Over Revolution

Key takeaways

  1. 01GPT-5.5 Instant is the new default model for all ChatGPT users, rolling out as of May 5th, 2026.
  2. 02OpenAI claims the model produces 52.5% fewer 'hallucinated claims' on sensitive prompts compared to its predecessor, GPT-5.3 Instant.
  3. 03The update also aims for more concise, 'to-the-point' responses and will use fewer 'gratuitous emojis'.
  4. 04Enhanced personalization features, including a 'memory sources' tool for transparency, are being introduced, starting with paid tiers.
  5. 05The previous model, GPT-5.3 Instant, will remain available for a three-month transition period before being retired.

A New Default ModelLede

On May 5th, OpenAI began updating ChatGPT with a new default model, GPT-5.5 Instant, designed to address one of the most persistent problems in generative AI: its tendency to fabricate information. The update is being deployed to all tiers of ChatGPT, including free users.[3] OpenAI states that its new GPT-5.5 Instant model demonstrates significant improvements in factuality across the board.[1] This move signals a clear focus on reliability as AI tools become more integrated into daily workflows.

Targeting FactualityEvent Summary

The core of the upgrade is a direct attempt to curb AI 'hallucinations.' In the company's internal tests, the new model produced 52.5% fewer fabricated statements on sensitive topics such as medicine, law, and finance compared to its predecessor.[2] Beyond factuality, OpenAI also reports that GPT-5.5 Instant delivers more direct, concise answers and avoids the use of what it calls gratuitous emojis. The rollout plan includes a three-month transition period where the previous model, GPT-5.3 Instant, will remain an option before it is retired, allowing users time to adjust to the changes.

A Push for TransparencyOutlook

This update appears to be a strategic effort to build user trust and directly counter a primary criticism of large language models. The emphasis on accuracy, especially in high-stakes domains, positions ChatGPT against competitors like Google's Gemini, which is also heavily investing in personalization and reliability.

A key component of this strategy is a new 'memory sources' function. This feature, rolling out to consumer plans, will permit the chatbot to reveal what context influenced its personalized answers, such as information from previous chats. It gives users the ability to delete or correct the information the model uses, offering a degree of transparency and control that has been largely absent from consumer AI products.

Refinement Over RevolutionWrapup

While not a generational leap in capability, the release of GPT-5.5 Instant appears to mark an important refinement in the evolution of AI assistants. The focus appears to be shifting from raw power to dependability and user safety. By making its flagship product more factual and its personalization mechanisms more transparent, OpenAI is addressing foundational issues that could otherwise hinder mainstream adoption. This incremental, safety-oriented approach may define the next stage of development for the entire generative AI sector.

Citations

  1. [1]

    OpenAI states that its new GPT-5.5 Instant model demonstrates “significant improvements in factuality across the board.”

    "OpenAI says its new GPT-5.5 Instant model has “significant improvements in factuality across the board.”"
    PressThe Vergetheverge.com
  2. [2]

    In the company's internal tests, the new model produced 52.5% fewer fabricated statements on sensitive topics such as medicine, law, and finance compared to its predecessor.

    "The company claims that, based on “internal evaluations,” GPT-5.5 Instant produced “52.5% fewer hallucinated claims” than its Instant model for GPT-5.3 “on high-stakes prompts covering areas like medicine, law, and finance.”"
    PressThe Vergetheverge.com
  3. [3]

    The update is being deployed to all tiers of ChatGPT, including free users.

    "The company announced in a blog post on Tuesday that ChatGPT 5.5 Instant has begun rolling out to all users as the new default model for the popular AI chatbot."
    PressMashablemashable.com

Sources

4 references

Other

Topics

  • ChatGPT
  • OpenAI
  • GPT-5.5 Instant
  • AI model
  • AI hallucinations
  • factuality
  • large language models
  • AI safety
  • generative AI
  • AppStore
Maxime Doussin, CTO at MWM

Maxime Doussin

CTO

Maxime Doussin is the CTO of MWM, where he leads engineering, data infrastructure, and the mobile-app market-intelligence platform. He writes MWM's weekly app trend analysis, drawing on proprietary ranking data covering millions of iOS and Android apps across 150+ countries.

This article is an independent editorial analysis. App names, trademarks, and brands mentioned are the property of their respective owners. Market data and rankings referenced are based on MWM's proprietary estimates.

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