The Tool Desk
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Set up custom instructions on your device
OpenAI’s current instructions use different menu labels on desktop and mobile. In either case, turn on Enable customization before entering text in the Custom Instructions field.
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Web and desktop
- Open ChatGPT and select Settings.
- Select Personalization.
- Turn on Enable customization.
- Enter your guidance in Custom Instructions.
iOS and Android
- Open ChatGPT’s Settings.
- Select Customize ChatGPT.
- Turn on Enable customization.
- Enter your guidance in the Custom Instructions field.
OpenAI says the changes take effect immediately across all chats. You can adjust or remove the instructions for future conversations. OpenAI’s Custom Instructions FAQ describes them as guidance about what ChatGPT should consider in its response.
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Use custom instructions for stable context and preferences that apply to many requests, not for a one-time task. Keep each preference concrete enough that you can tell whether a response followed it.
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- Relevant context: State your role, experience level, or recurring work when that changes the kind of explanation you need.
- Common tasks: Mention the kinds of help you often request, such as explaining technical concepts or organizing a plan.
- Response style: Specify a preferred tone, level of detail, or length.
- Formatting: Ask for a particular structure when useful, such as numbered steps for procedures or a short summary before detail.
- Uncertainty: Say whether you want ChatGPT to ask clarifying questions or clearly identify assumptions when details are missing.
For example, a useful instruction might be: “I’m new to networking. Explain unfamiliar terms briefly, use numbered steps for setup instructions, and ask a clarifying question if my device or operating system would change the answer.” This is practical guidance, not a guarantee that every answer will be more accurate or useful.
Check your plan’s character limit
OpenAI’s Help Center lists different saved-character limits by plan. These are the documented limits as reported on the help page updated around August 2026; the limit shown in your ChatGPT interface is the best check if it differs.
| Plan | Custom instructions limit |
|---|---|
| Free and Go | Up to 1,500 characters |
| Plus, Pro, Enterprise, Business, and Education | Up to 5,000 characters |
Source: OpenAI Help Center.
Know how instructions relate to Memory and other personalization settings
These controls can complement one another, but they serve different purposes.
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| Feature | 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 | Adjusts presentation traits such as warmth, enthusiasm, formatting, and emoji use. OpenAI says it works alongside personality, custom instructions, and saved memories. |
| Personality | Selects a broader response style and tone; OpenAI says it works alongside custom instructions and memories without changing ChatGPT’s capabilities or safety rules. |
For Characteristics, OpenAI’s help page gives the path profile icon → Personalization → Characteristics on web, iOS, and Android. Memory and personalization options may vary with account and workspace settings. Sources: Memory, Characteristics, and Personality.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Understand old chats, exports, and Temporary Chat
Updating or removing instructions changes future conversations, but earlier versions may still appear in previous chat history. OpenAI 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; its Custom Instructions FAQ points to data-use controls for details.
Temporary Chat has two personalization choices at the start:
- Personalized: May use existing custom instructions, memory, and plugins.
- Unpersonalized: Does not use those features.
Choose before sending the first message; OpenAI says the choice cannot be changed after the conversation starts. See OpenAI’s Temporary Chat FAQ.
Custom instructions in ChatGPT are not an API setting
OpenAI says it will not provide an API for the ChatGPT custom-instructions interface. For similar guidance in an API integration, OpenAI points developers to system messages instead. See the Custom Instructions FAQ.
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