How to Access Legacy ChatGPT Models

As OpenAI continues to iterate and release new versions of ChatGPT, users may wish to access previous models for comparison, validation, or familiarity. Fortunately, ChatGPT provides an option to enable “Legacy Models,” allowing access to earlier versions such as GPT-4o. This functionality is particularly valuable for engineering teams and technical professionals who rely on consistent model behavior for prompt workflows.

Key Features and Benefits:

• Restores access to previous versions that may better suit specific tasks or workflows

• Enables comparative testing between different model generations

• Supports consistent AI engineering by minimizing variability in model behavior

Limitations to Consider:

• Access to legacy models may require a ChatGPT Plus subscription

• The feature’s location or availability may change over time

• Older models may yield different outputs, requiring prompt recalibration

At Singularity, this feature is routinely used to:

• Re-test AI outputs and calculations using previously stable versions like GPT-4o

• Assess changes in hallucination rates or structure across versions

• Maintain reliability in automation and prompt workflows where output consistency is critical

Step-by-Step Instructions:

1. Log into your ChatGPT account at chat.openai.com

2. Click your profile icon in the bottom-left corner and open Settings

3. Toggle on the “Show Legacy Models” option

4. Return to the main chat screen and click the model name at the top

5. Under “Legacy Models,” select GPT-4o or any other available previous version

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