· AI Seedling · Beginner Guides · 10 min read
ChatGPT Custom Instructions: How to Set Them Up and When to Use Them
Custom Instructions tell ChatGPT your preferences once and apply them to every conversation. Here is how to enable, edit, and disable them on any device.
Custom Instructions let you tell ChatGPT what to consider in every response, without repeating yourself in each conversation. To enable them on web or desktop, open Settings > Personalization > Custom Instructions, toggle Enable customization on, and enter your instructions. On iOS or Android, open Settings > Customize ChatGPT and do the same. Your instructions apply immediately to all chats, including existing conversations.
The details in this guide follow OpenAI’s Custom Instructions documentation, checked November 2, 2026. The page was updated by OpenAI within the past week.
What Custom Instructions are
Custom instructions are text you write once that ChatGPT applies to every conversation. They are different from prompts, which you type into individual chats. A prompt is a one-time request. A custom instruction is a standing preference.
For example, if you want ChatGPT to always explain things in simple terms because you are not a technical user, you can write that as a custom instruction. Every response in every new or existing conversation will then follow that guidance without you asking again.
Custom instructions allow you to share anything you’d like ChatGPT to consider in its response. Your custom instructions are applied immediately to all chats.
Source: OpenAI, ChatGPT Custom Instructions, checked November 2, 2026.
Custom instructions are available on all plans — Free, Go, Plus, Pro, Enterprise, Business, and Education — on Web, Desktop, iOS, and Android.
How to enable Custom Instructions
On web and desktop
- Open Settings.
- Select Personalization.
- Select Custom Instructions.
- Toggle Enable customization on.
- Enter your instructions in the Custom Instructions field.
On iOS and Android
- Open Settings.
- Select Customize ChatGPT.
- Toggle Enable customization on.
- Enter your instructions in the Custom Instructions field.
Updates to custom instructions settings are applied immediately across all chats. You do not need to start a new conversation for the changes to take effect. If you edit your instructions mid-conversation, the next response in that same conversation will use the updated version.
How to disable Custom Instructions
Disabling stops your instructions from applying to future conversations. It does not remove instructions from past conversations.
On web and desktop
- Open Settings > Personalization > Custom Instructions.
- Toggle Enable customization off.
- Optionally, delete your instructions from the text field.
On iOS and Android
- Open Settings > Customize ChatGPT.
- Toggle Enable customization off.
- Optionally, delete your instructions from the text field.
You can leave the text in place and just toggle off if you want to temporarily pause customization without losing your written instructions. Toggle it back on when you want to resume.
What to write in Custom Instructions
There is no required format. Write in plain language what you want ChatGPT to consider. The field accepts free text, so you can include multiple preferences separated by line breaks.
Practical examples that beginners find useful:
- “I am new to AI tools. Explain technical terms when you use them.”
- “Keep responses short unless I ask for detail.”
- “I prefer bullet points over long paragraphs.”
- “I work in real estate. Tailor examples to that industry when relevant.”
- “I am not a native English speaker. Use simple vocabulary.”
Avoid putting information in custom instructions that you would not want shared. If you use third-party plugins, the model may provide plugin developers with relevant information from your instructions. Only use plugins that you trust, and do not include anything you would not want to give to a third-party plugin developer.
Character limits by plan
The amount of text you can save in custom instructions depends on your plan.
| Plan | Character limit |
|---|---|
| Free and Go | 1,500 characters |
| Plus, Pro, Enterprise, Business, Education | 5,000 characters |
Source: OpenAI, ChatGPT Custom Instructions, checked November 2, 2026.
For comparison, 1,500 characters is roughly 250 words — about the length of this section. 5,000 characters is roughly 800 words. Most beginners do not need more than a few sentences of instructions.
Custom Instructions vs Memory
These two features overlap in purpose but work differently. Confusing them leads to expecting one to do the other’s job.
| Feature | What it is | How it changes | Where to manage |
|---|---|---|---|
| Custom Instructions | Direct guidance you write | Stays the same until you edit it | Settings > Personalization > Custom Instructions |
| Memory | Information ChatGPT gathers from conversations | Changes over time as context changes | Settings > Personalization > Memory |
Custom instructions are always active when enabled. You wrote them, so you know exactly what they say. Memory is selective and evolves. You may not know exactly what ChatGPT remembers without checking.
OpenAI’s documentation makes the distinction explicit:
Custom instructions are direct guidance that you provide about what ChatGPT should know and how it should respond. Memory can use relevant information that develops across conversations and other available sources.
Source: OpenAI, Memory in ChatGPT, checked November 2, 2026.
A practical approach: use custom instructions for preferences that rarely change (your communication style, your expertise level). Use Memory for facts that emerge across conversations (your project details, your past questions). See the ChatGPT Memory guide for how to manage the Memory side.
Custom Instructions vs project instructions
If you use ChatGPT Projects, each project can have its own instructions. Project instructions override your global custom instructions when you are working within that project.
This means custom instructions are your default for general conversations. Project instructions are specific overrides for a defined workspace. If your global instruction says “keep responses short” but a project instruction says “provide detailed analysis,” the project instruction wins inside that project.
How your data is used
OpenAI’s documentation lists four data-use points that are worth reading carefully:
You can edit or delete custom instructions at any time for future conversations.
Your instructions won’t be shared with shared link viewers.
If you use third party plug-ins, then the model may provide plug-in developers with relevant information from your instructions. Only use plug-ins that you trust, and don’t share any information you don’t want to give to third party plug-in developers.
Information from your use of custom instructions will also be used to improve model performance – like teaching the model how to adapt its responses to your instructions without overdoing it.
Source: OpenAI, ChatGPT Custom Instructions, checked November 2, 2026.
The third point is the one most people miss. If you write sensitive information in custom instructions and then use a third-party plugin, that information may reach the plugin developer. Treat custom instructions the same way you would treat a profile on any online service: do not put passwords, account numbers, or other secrets in them.
The fourth point means that your instructions contribute to model training unless you opt out. You can opt out of having your content used to improve model performance through the Data controls settings. See OpenAI’s data usage guide for details.
What happens to Custom Instructions when you delete your account
When you delete your OpenAI account, custom instructions tied to your account are deleted within 30 days as part of that process. However, if you have not opted out of model improvement, OpenAI may retain de-identified and disassociated chat records.
If you update or remove your custom instructions, previous versions continue to appear in your chat history. The old instructions were part of past conversations, and updating the setting does not retroactively change what was already said. To remove old instructions from previous conversations, clear those conversations from your chat history.
For the full account deletion process, see the ChatGPT account deletion guide.
Are Custom Instructions included in data exports
Yes. When you request a ChatGPT data export, your custom instructions are included in the download. This means you can review them offline or transfer them to another account by copying the text. The request steps and the 24-hour download window are in How to Export Your ChatGPT Data.
The data export is another copy you must protect. If your custom instructions contain personal preferences or workplace details, the export file should be stored securely, not left in a downloads folder on a shared device.
Custom Instructions in the API
There is no separate API for custom instructions. If you are building an application using the Chat Completions API, use the system message to achieve a similar effect. The system message lets you set context and instructions for the model in the same way that custom instructions do in the ChatGPT interface.
OpenAI’s prompt engineering guide covers how to structure system messages effectively. This is relevant only if you are developing with the API. If you only use ChatGPT through the web or mobile app, this section does not apply.
A five-minute Custom Instructions exercise
Set up one simple instruction and observe its effect.
- Open Settings > Personalization > Custom Instructions.
- Toggle Enable customization on.
- Type: “I am practicing with AI tools. Give me a one-sentence summary at the start of each response, then the details.”
- Save and start a new chat.
- Ask: “What are three uses for a spreadsheet?”
- Read the response and check whether it starts with a one-sentence summary.
- Return to Settings and try changing the instruction to: “Always answer in exactly three bullet points.”
- Ask the same question in a new chat and compare the format.
The goal is to see how a single sentence changes the shape of a response. If the format does not match your instruction, check whether you saved the changes and whether Enable customization is still on.
After the exercise, decide whether to keep, edit, or disable the instruction. A preference that helps in practice may be distracting in real use. There is no penalty for turning it off.
Questions beginners often ask
Are Custom Instructions the same as prompts?
No. A prompt is what you type in a single conversation. Custom instructions are standing preferences that apply to every conversation. You can use both: custom instructions set your general preferences, and prompts ask specific questions.
Do Custom Instructions work on the free plan?
Yes. Custom instructions are available on all plans, including Free and Go. The character limit is 1,500 characters on Free and Go, and 5,000 characters on Plus, Pro, Enterprise, Business, and Education.
Can I use Custom Instructions and Memory at the same time?
Yes. They are separate features that can both be enabled. Custom instructions provide direct guidance you wrote. Memory provides information ChatGPT gathers from conversations. Both can shape responses simultaneously.
Will people see my Custom Instructions if I share a chat link?
No. Your custom instructions are not shared with shared link viewers. However, if you use third-party plugins, plugin developers may receive relevant information from your instructions. Do not put sensitive information in custom instructions if you use plugins. For what a link does expose — mainly the conversation content itself — see ChatGPT Shared Links.
Do Custom Instructions apply to past conversations?
Updates to custom instructions apply immediately to all chats, including existing conversations. However, if you change or remove instructions, previous versions remain in past chat history. The old instructions were part of those conversations when they happened.
When to ask a person
If your custom instructions involve workplace policies, client confidentiality, or regulated information, check with your administrator or compliance team before entering details that describe internal processes. Custom instructions are a personal setting, not an enterprise policy tool.
Keep learning in small steps
Compare custom instructions with ChatGPT Memory and Temporary Chat to understand which personalization control fits each situation. The prompt writing guide covers how to write effective individual prompts. You can also take the AI level test to find a practical habit to work on next.
A final reminder
Custom Instructions are a small setting with a large effect. Write one sentence today, test it, and adjust before adding more.
