The Tool Desk
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Set up custom instructions on your device
- On web or desktop: Open Settings, choose Personalization, and make sure Enable customization is on.
- On iOS or Android: Open Settings, choose Customize ChatGPT, and make sure Enable customization is on.
- Enter your guidance in the Custom Instructions field and save or leave the settings screen as prompted.
The labels can change as ChatGPT is updated. If the path differs in your app, look in Settings for Personalization or Customize ChatGPT. OpenAI’s Custom Instructions FAQ says edits apply immediately across chats. You can adjust or remove instructions for future conversations.
What to write for more useful answers
Use custom instructions for stable context and preferences that are relevant across many conversations—not a detailed prompt for just one task. Make each preference concrete enough that you can tell whether ChatGPT followed it.
- Relevant context: State your role, experience level, or recurring situation when it changes the kind of answer you need.
- Common tasks: Name the work you often ask ChatGPT to help with, such as troubleshooting, planning, or explaining technical topics.
- Response style: Specify a tone, approximate level of detail, or preferred format, such as concise explanations with steps.
- Handling uncertainty: Say whether you want clarifying questions when key details are missing, or assumptions explicitly identified.
For example, “I’m new to home networking. For troubleshooting, give numbered steps and explain unfamiliar terms. Ask for my router model if it matters; otherwise state your assumptions.” This is practical guidance, not a guarantee that every answer will match your preferences. Keep instructions focused: a short set of actionable preferences is easier to apply than a long list of broad requests.
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Check your plan’s character limit
OpenAI’s Help Center lists different saved-character limits by plan. The figures below are the limits reported on its page in 2026; check the field in your account if its displayed limit differs.
| Plan | Saved-character limit |
|---|---|
| Free and Go | Up to 1,500 characters |
| Plus, Pro, Enterprise, Business, and Education | Up to 5,000 characters |
These are limits for saved custom instructions, not a measure of how much they improve responses. OpenAI’s current plan grouping and limits are documented in its Custom Instructions FAQ.
Know how custom instructions differ from other personalization settings
ChatGPT has several personalization controls. They can work together, but they address different needs.
| Control | What it does |
|---|---|
| Custom instructions | Explicit guidance you provide about what ChatGPT should know and how it should respond. |
| Memory | May retain relevant preferences and details from conversations and other available sources. Features and controls can vary by plan, region, platform, and workspace settings. |
| Characteristics | Lets you adjust response traits such as warmth, enthusiasm, formatting, and emoji use. OpenAI says it works alongside personality, custom instructions, and saved memories. |
| Personality | A broader response style and tone. OpenAI says it works with custom instructions and memories but does not change ChatGPT’s capabilities or safety rules. |
In short, use custom instructions for personal guidance, Memory for context ChatGPT may retain, and Characteristics or Personality to tune presentation style. OpenAI explains Memory, Characteristics, and Personality in separate Help Center articles.
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What changes mean for existing chats and data
OpenAI says an instruction update takes effect immediately across chats, but the previous wording may remain in the history of older conversations. The FAQ says you can clear relevant conversations to remove those historical copies. Custom instructions are also included in ChatGPT data exports. OpenAI says information from their use is used to improve model performance; see its FAQ for details and links to data-use controls.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Choose personalization for a Temporary Chat before starting
At the start of a Temporary Chat, you can choose Personalized or Unpersonalized. A Personalized Temporary Chat can use existing custom instructions, memory, and plugins; an Unpersonalized one does not use those features. OpenAI says this choice is made before the first message and cannot be changed after the conversation starts. See the Temporary Chat FAQ.
Custom instructions in ChatGPT’s API
The UI custom-instructions setting is not an API feature. OpenAI’s FAQ says there will be no API for it and points developers to API system messages as a way to achieve a similar effect. See the Custom Instructions FAQ.
Quick Recap
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