How to set it up.

1. Click on "Projects" in the left sidebar and select "Create New Project."
2. Give your project a name (e.g., "Q3 Marketing Campaign" or "Mobile App Redesign").
3. Click the three-dot menu in your Project → "Project settings" to add project instructions that apply only within this project .
4. Upload reference files such as PDFs, notes, or spreadsheets .
5. Enable project-only memory in the project settings to keep context contained .

When to use it.

• You have one or more related projects that each need their own isolated context.
• You want to upload project-specific files and have ChatGPT reference them across multiple chats.
• You want to avoid spilling project details into unrelated conversations.

Method 2: Memory (Best for Cross-Project, General Context)

What it does. Memory is what helps ChatGPT learn your preferences, projects, and constraints across all conversations . When enabled, ChatGPT can automatically remember relevant details, such as your name, preferred tone, ongoing goals, and constraints .

Recent improvements. In April 2025, OpenAI introduced "Dreaming" — a background process that allows ChatGPT to automatically curate memories by referencing chat history, rather than relying only on explicitly saved memories . As of June 2026, Dreaming V3 further improved context freshness and accuracy . Plus and Pro users now have twice the memory capacity, and memories are updated automatically to reduce stale or contradictory information .

How to set it up.

1. Go to Settings → Personalization.
2. Toggle on "Memory."
3. You can view, manage, and delete specific memories from the same panel .
4. Optionally, turn on "Saved memories" to explicitly record important facts (e.g., "Remember I'm a vegetarian") .

When to use it.

• You want ChatGPT to learn your preferences gradually across all conversations.
• You work on multiple unrelated topics and want general context (e.g., your job role, writing style, favorite tools) to apply everywhere.
• You're okay with ChatGPT automatically surfacing context from past chats.

Method 3: Custom Instructions (Best for Fixed, Manual Rules)

What it does. Custom Instructions let you provide direct guidance that applies across every chat . Think of it as handing ChatGPT a written note explaining who you are, what you want, and how you'd like it to respond . Unlike Memory, Custom Instructions are explicit and don't change based on conversation history unless you update them manually.

Important caveat. Project instructions will override global Custom Instructions when you're working inside a Project . If you want specific rules for a single project, use the project's own instructions instead.

How to set it up.

1. Go to Settings → Personalization.
2. Click on "Custom Instructions."
3. Fill in the fields (e.g., "I'm a software engineer working on a Python project. Please assume I have intermediate coding knowledge.") .
4. Save. These instructions will apply to all new chats.

When to use it.

• You have stable, explicit rules that should apply everywhere (e.g., preferred terminology, response format, or constraints).
• You don't want ChatGPT to infer these rules from conversation history.
• You want a simple, manual override that doesn't require managing a separate project.

Quick Decision Guide

Summary

For most project work, creating a Project and adding project instructions plus project-only memory is the most reliable way to keep context organized and scoped across multiple related chats . If you need context to carry across unrelated topics, turn on Memory. For manual rules that don't change, stick with Custom Instructions. Each tool serves a distinct purpose, and you can even combine them — for example, using Memory to automatically learn your general preferences while using Projects to keep each project's context isolated.

How to set it up.

1. Click on "Projects" in the left sidebar and select "Create New Project."
2. Give your project a name (e.g., "Q3 Marketing Campaign" or "Mobile App Redesign").
3. Click the three-dot menu in your Project → "Project settings" to add project instructions that apply only within this project .
4. Upload reference files such as PDFs, notes, or spreadsheets .
5. Enable project-only memory in the project settings to keep context contained .

When to use it.

• You have one or more related projects that each need their own isolated context.
• You want to upload project-specific files and have ChatGPT reference them across multiple chats.
• You want to avoid spilling project details into unrelated conversations.

Method 2: Memory (Best for Cross-Project, General Context)

What it does. Memory is what helps ChatGPT learn your preferences, projects, and constraints across all conversations . When enabled, ChatGPT can automatically remember relevant details, such as your name, preferred tone, ongoing goals, and constraints .

Recent improvements. In April 2025, OpenAI introduced "Dreaming" — a background process that allows ChatGPT to automatically curate memories by referencing chat history, rather than relying only on explicitly saved memories . As of June 2026, Dreaming V3 further improved context freshness and accuracy . Plus and Pro users now have twice the memory capacity, and memories are updated automatically to reduce stale or contradictory information .

How to set it up.

1. Go to Settings → Personalization.
2. Toggle on "Memory."
3. You can view, manage, and delete specific memories from the same panel .
4. Optionally, turn on "Saved memories" to explicitly record important facts (e.g., "Remember I'm a vegetarian") .

When to use it.

• You want ChatGPT to learn your preferences gradually across all conversations.
• You work on multiple unrelated topics and want general context (e.g., your job role, writing style, favorite tools) to apply everywhere.
• You're okay with ChatGPT automatically surfacing context from past chats.

Method 3: Custom Instructions (Best for Fixed, Manual Rules)

What it does. Custom Instructions let you provide direct guidance that applies across every chat . Think of it as handing ChatGPT a written note explaining who you are, what you want, and how you'd like it to respond . Unlike Memory, Custom Instructions are explicit and don't change based on conversation history unless you update them manually.

Important caveat. Project instructions will override global Custom Instructions when you're working inside a Project . If you want specific rules for a single project, use the project's own instructions instead.

How to set it up.

1. Go to Settings → Personalization.
2. Click on "Custom Instructions."
3. Fill in the fields (e.g., "I'm a software engineer working on a Python project. Please assume I have intermediate coding knowledge.") .
4. Save. These instructions will apply to all new chats.

When to use it.

• You have stable, explicit rules that should apply everywhere (e.g., preferred terminology, response format, or constraints).
• You don't want ChatGPT to infer these rules from conversation history.
• You want a simple, manual override that doesn't require managing a separate project.

Quick Decision Guide

Summary

For most project work, creating a Project and adding project instructions plus project-only memory is the most reliable way to keep context organized and scoped across multiple related chats . If you need context to carry across unrelated topics, turn on Memory. For manual rules that don't change, stick with Custom Instructions. Each tool serves a distinct purpose, and you can even combine them — for example, using Memory to automatically learn your general preferences while using Projects to keep each project's context isolated.