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To customize an AI assistant, choose the feature that matches where you want your preference to apply: account-wide instructions for ordinary chats, memory for context drawn from past interactions, project settings for ongoing work, reusable assistants for recurring tasks, or style controls for tone and format. ChatGPT, Gemini, and Claude each divide these jobs differently, and some features depend on your account, plan, region, or workspace.
Choose the right kind of customization
Customization is not one setting. An instruction you write yourself is different from information an assistant recalls from earlier chats, and both differ from a project’s files or a reusable task setup.
| What you want | Use this kind of feature | What to expect |
|---|---|---|
| Preferences to apply across ordinary chats | Account-level instructions or profile preferences | You state the guidance directly; it applies broadly where supported. |
| Relevant details recalled from earlier conversations | Memory or past-chat personalization | The assistant may use context from previous chats or other available sources. Review the feature’s controls and prerequisites. |
| Context for one continuing project | Project instructions and materials | Keep related chats, files, and guidance together; project rules may take precedence over global guidance. |
| A repeated specialized task | A reusable assistant or Gem | Save task-specific directions so you do not have to rebuild them each time. |
| A preferred voice or response format | Style controls, where available | Specify tone and presentation separately when the service offers dedicated controls. |
Start with the narrowest scope that fits. Use global instructions for stable preferences, a project for work with its own source material, and a reusable assistant for a repeated procedure. Memory is useful for relevant context, but it is not a substitute for explicit instructions when a requirement must be consistent.
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Set account-wide Custom Instructions
Custom Instructions are direct guidance for how ChatGPT should respond, rather than information inferred from prior conversations. On web or desktop, go to Settings → Personalization. On iOS or Android, go to Settings → Customize ChatGPT. OpenAI says the feature is available on all plans across web, desktop, iOS, and Android; its help page lists a 1,500-character limit for Free and Go users and 5,000 characters for Plus, Pro, Enterprise, Business, and Education users. See OpenAI’s Custom Instructions guide for current details.
#1 Best Overall
Write guidance that is specific and easy to apply. For example: “Use plain English, explain unfamiliar technical terms, and give numbered steps when describing a procedure. Put the direct answer first.” You can edit or remove the instructions, and OpenAI says changes apply immediately to chats.
Use Memory for relevant context from chats
Memory is separate from Custom Instructions. OpenAI describes it as using relevant preferences and details that develop from chats and other available sources. Depending on availability, those sources may include past chats, saved memories, files, or connected-app content. Controls and availability can vary by plan, region, platform, and workspace; consult OpenAI’s Memory guide for the current options.
Review what is remembered and use the available controls to manage it. Turning Memory off does not delete past chats, and deleting information can require action in the place where it is stored. Treat memory as context that may help personalize responses, not as a guarantee that every preference will be applied in every conversation.
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Keep ongoing work in a Project
Projects group related chats, files, and instructions. Use one when a body of work needs its own source materials or rules—for example, a research project with a fixed set of reference documents. Project instructions apply within that project and override global Custom Instructions there. Availability and sharing depend on plan and workspace settings. See OpenAI’s Projects guide.
Customize Gemini
Set Instructions for Gemini
Google’s Instructions for Gemini let you request response preferences, such as beginning with a short summary or using bullets for long passages. On desktop, the documented route is Settings & help → Personal Intelligence → Instructions for Gemini. The feature requires a personal Google Account; it is not available for work, school, or supervised accounts, and Google lists feature exceptions, including Gems. You can edit, delete, or switch instructions off. Google also cautions that instructions to forget or avoid topics may not always work perfectly. Check Google’s Instructions for Gemini help page for current availability and behavior.
Use a Gem for repeatable tasks
A Gem is a customized version of Gemini for a specific goal or recurring job. It is a better fit than general instructions when you want a reusable set of task directions, such as a consistent process for turning notes into a structured summary. Google explains the feature in its guides to using Gems and getting started with Gems.
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Enable past-chat personalization only if eligible
Gemini’s personalization with memory of past chats is distinct from Instructions for Gemini and from Gems. Google says it requires users to be 18 or older, a personal Google Account, and Keep Activity enabled. It is unavailable in some features, including Gems and Live chats, and can be turned off. See Google’s past-chat personalization help page for the current requirements.
Customize Claude
Set profile preferences for conversations
Claude profile preferences apply across conversations, making them the place for stable account-wide guidance. Use them for preferences such as how much background to include or how to organize an answer.
Use Project instructions for focused work
Project instructions apply to chats in a particular Claude project. Put project-specific requirements and context there rather than making them global. Anthropic’s personalization guide says Projects are currently available to users on paid Claude plans; check Anthropic’s Claude personalization guide for current availability.
Choose a Style for tone and format
Claude Styles adjust response tone and format, including custom communication patterns. Use a style when the main change you want is how an answer sounds or is presented, rather than which project facts Claude should use.
Do not confuse past-chat search with profile preferences
Anthropic’s guide describes past-chat search as rolling out to certain plans, including Max, Team, and Enterprise, with expansion planned. This feature is time-sensitive and is not the same as account-wide profile preferences. Check the current guide and your account before relying on it.
Write instructions that work across tools
Clear customization gives an assistant something observable to do. A useful instruction identifies the audience, output, and constraints instead of relying on vague requests such as “be better” or “sound professional.”
Best Value
- State the default: “Assume I am comfortable with basic spreadsheet formulas.”
- Name the format: “For procedures, use numbered steps and include the menu path.”
- Specify tone in practical terms: “Be concise and direct; define specialized terms on first use.”
- Give a rule for uncertainty: “If a key detail is missing, ask one clarifying question rather than inventing it.”
- Keep project-only rules local: Put a client’s terminology or a project’s source restrictions in its project instructions, not in your general preferences.
After saving instructions, test them with a representative request. If the result misses the mark, revise one instruction at a time so you can tell which change helped. For requirements that matter, include them in the relevant project or task prompt rather than depending only on recalled context.
Check availability and controls before relying on a feature
Product labels, settings paths, eligibility, and feature behavior change. An option may differ by plan, account type, region, age, platform, or workspace policy, and a feature can be unavailable in a particular mode such as a Gem or Live chat. Open the relevant vendor help page and the live settings in your own account before building a workflow around it.
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