chatgpt-custom-instructions
ITIAN ChatGPT Academy
Technology Simplified — Solutions That Work
Custom Instructions
Give ChatGPT clear, reusable guidance about your needs and preferred working style—without repeating the same background at the start of every conversation.
Learning Outcomes
By the end of this lesson, you should be able to:
Explain Their Purpose
Describe Custom Instructions as explicit, reusable guidance that ChatGPT considers across chats.
Write Useful Guidance
Create concise instructions about context, communication, workflow, quality and boundaries.
Protect Private Information
Recognise what should never be placed in persistent instructions or sent to third-party tools.
Test and Improve
Use representative prompts to find vague, conflicting or overly restrictive instructions.
Custom Instructions are your reusable briefing note
They tell ChatGPT what you want it to consider in its responses. They are best for stable, explicit preferences—such as your language convention, experience level, learning style and preferred response structure.
They are not a password manager, a complete biography, a project archive or a replacement for a clear task prompt.
What Belongs in Custom Instructions?
| Category | Useful content | Example |
|---|---|---|
| Relevant context | Role, experience and recurring needs that affect answers | “I am learning website development and prefer beginner-friendly explanations.” |
| Language and tone | Stable writing conventions and communication preferences | “Use New Zealand English and a warm, professional tone.” |
| Teaching method | How explanations should be structured | “Teach step by step, explain unfamiliar terms and include a small example.” |
| Output format | Common formatting that improves usability | “Lead with the outcome, then provide numbered steps and a verification checklist.” |
| Quality rules | Recurring standards for accuracy and accessibility | “Flag assumptions and use accessible, semantic HTML when producing web pages.” |
| Boundaries | How to handle uncertainty or missing information | “Do not invent missing facts; say what should be checked.” |
What Should Stay Somewhere Else?
Passwords and Secrets
Never include passwords, authentication codes, private keys, financial credentials or confidential access information.
One-Off Requests
A temporary tone, format or exception belongs in the current prompt—not in instructions that affect other chats.
Project-Only Rules
Brand colours, page slugs, client requirements and project files belong in the relevant Project instructions and reference material.
Unnecessary Personal Detail
Include only information that genuinely improves responses and that you are comfortable using for personalisation.
Enable or Edit Custom Instructions
Web and Desktop
Open Settings → Personalization, ensure Enable customization is on, then open Custom Instructions.
iOS and Android
Open Settings, select Customize ChatGPT, turn on Enable customization and enter your instructions.
Review Before Saving
Remove private data, repeated guidance and project-only rules. The longer-form fields currently allow up to 1,500 characters.
Save and Test
Changes apply immediately across chats, including existing conversations. Test several different tasks.
Refine One Rule
If results are inconsistent, rewrite one vague instruction rather than adding several new ones.
Disable When Needed
Turn Enable customization off for a broader test. Deleting text is optional, but disabling is not the same as erasing prior chat content.
The ITIAN Five-Part Formula
1. Context
Only the recurring facts that change what a useful answer looks like.
2. Goal
The broad outcomes you regularly work towards or want help learning.
3. Communication
Language, tone, assumed experience and explanation depth.
4. Workflow
How you prefer tasks to be planned, completed and verified.
5. Quality and Boundaries
Standards to follow and what to do when information is uncertain or missing.
Write instructions, not aspirations
“Be excellent” is difficult to apply. “Lead with the answer, explain unfamiliar terms, provide numbered steps and flag assumptions” describes observable behaviour that can be tested.
Interactive Custom Instructions Builder
Create a concise draft locally. Entries are not transmitted or saved by this page. Do not enter confidential or highly sensitive information.
0 / 1,500 characters
Example Profiles
Use these as patterns, not text that must be copied word for word.
Step-by-Step Learner
“I am learning new technology and may not know specialist terms. Use New Zealand English. Lead with the outcome, then explain each step clearly. Define unfamiliar terms, include a small example and finish with a short verification checklist. If information is uncertain, say what needs checking.”
Photography Workflow
“I work with landscape and travel photography. Explain editing decisions in practical visual terms. When suggesting a workflow, preserve original files, distinguish creative choices from technical corrections and provide Lightroom or Photoshop steps in order.”
Small Business Owner
“I need practical guidance for a small New Zealand business. Use plain language, state assumptions and distinguish general information from professional legal, tax or financial advice. Prioritise low-complexity actions and explain cost, time and risk trade-offs.”
Website Builder
“When producing web pages, use semantic HTML, responsive CSS, accessible labels, visible keyboard focus and SEO-friendly structure. Provide complete code when requested. Preserve supplied content and design authority, and explain any recommended change before making it.”
Improve Weak Instructions
| Weak instruction | Why it struggles | Stronger version |
|---|---|---|
| “Always be perfect.” | Impossible to test and encourages false confidence. | “Flag uncertainty, separate facts from assumptions and identify claims that should be verified.” |
| “Give detailed answers.” | “Detailed” means different things for different tasks. | “For unfamiliar topics, give a short overview, numbered steps, one example and a verification checklist.” |
| “Know my business.” | Does not supply relevant context or boundaries. | “I operate a small New Zealand service business; explain practical trade-offs and identify where professional advice is required.” |
| “Use my website style.” | The style is not defined and may be project-specific. | Put the exact design rules and authoritative template in that website’s Project. |
Test Before You Trust the Setup
Explanation Test
Ask for a beginner explanation. Check language, depth, examples and jargon.
Writing Test
Request a short email. Check whether task-specific tone still takes priority.
Planning Test
Ask for a simple plan. Check steps, assumptions, risks and next actions.
Boundary Test
Give incomplete information. Check that ChatGPT asks or flags uncertainty rather than inventing facts.
Unrelated Task Test
Try a topic outside your main work. Check that global instructions do not create irrelevant content.
Refinement Test
Change one instruction, repeat the same prompts and compare the results.
Privacy and Data Awareness
Use Minimum Necessary Detail
Include the smallest amount of personal or organisational context needed to improve routine responses.
Review Connected Tools
Official guidance notes that relevant information may be provided to third-party plugin developers when those tools are used. Use only tools you trust.
Know What Is Exported
Custom Instructions are included in your ChatGPT data export. Treat them as account data, not private scratch notes.
Control Model Improvement
Review Data Controls if you do not want eligible consumer content used to improve models. Managed workspace policies may differ.
Recommended: 16:9 • Captioned • Privacy review included
Future Guided Demonstration
This video will show the complete workflow using a fictional learner profile.
- Separate global from project-only guidance.
- Build a draft within the character limit.
- Test several task types.
- Remove conflicts and private details.
Practical Activity: Custom Instructions Audit
Complete each check before relying on your new setup.
0 of 10 completed — begin with relevant recurring context.
Knowledge Check
Answer all five questions, then check your result.
Official Sources and Further Reading
Reviewed against current first-party OpenAI guidance on 13 July 2026.
OpenAI guidance used in this lesson
- ChatGPT Custom Instructions — availability, settings, limits and data considerations.
- Is Memory different from Custom Instructions? — explicit instructions compared with remembered conversational context.
- Customising your ChatGPT personality — interaction between Personality, instructions and memories.
- Data Controls FAQ — controls for how eligible conversations are used.
Lesson Summary
Seven ideas to remember
- Use Custom Instructions for stable, explicit guidance across chats.
- Include only recurring context that materially improves answers.
- Describe observable communication, workflow and quality preferences.
- Keep one-off requirements in the prompt and project rules in the Project.
- Never store passwords, credentials or highly sensitive information.
- Stay within the current 1,500-character limit for longer-form fields.
- Test representative tasks and refine one instruction at a time.