# How to set custom instructions in ChatGPT on Mac: 2026 steps for both apps

> Learn how to set custom instructions in ChatGPT on Mac, in the Classic app and the new desktop app, with menu paths, limits and fixes for 2026.

URL: https://www.lazur.app/how-to/set-custom-instructions-in-chatgpt
Updated: 2026-11-09

To set custom instructions in ChatGPT on Mac, open ChatGPT > Settings, choose Personalization, then open Customize ChatGPT and type your instructions. In the newer ChatGPT desktop app, Settings opens with ⌘, but personal instructions live in an AGENTS.md file instead.

## Quick answer

- In the older ChatGPT Mac app, go to ChatGPT > Settings > Personalization > Customize ChatGPT, then fill in the fields.
- In the new ChatGPT desktop app, Settings opens with ⌘, and personal instructions are stored in AGENTS.md.
- Free and Go accounts get 1,500 characters per field, and paid plans are reported at 5,000.
- If new chats ignore your instructions, switch Enable for new chats off and on, then save and test again.

Applies to: ChatGPT Classic and the new ChatGPT desktop app on Apple silicon Macs with macOS 14 or later. Time: 5 min. Difficulty: Easy.

## What you need

- A Mac with an Apple silicon chip, M1 or newer, for the ChatGPT Mac app
- macOS 14 Sonoma or later
- A ChatGPT account, since instruction limits differ by plan
- A few minutes to write short sentences for each field

## How to Set custom instructions in ChatGPT on a Mac in ChatGPT on a Mac

1. **Open ChatGPT and confirm which app you have.** Open ChatGPT from Applications or the Dock. If the app is called ChatGPT Classic, follow the Classic path in these steps. If it is the new desktop app, use the new app steps at the end. Tip: Both apps can sit in Applications at the same time, so check the name before you follow a path.
2. **Open the Settings window.** (ChatGPT > Settings) Click ChatGPT in the menu bar at the top of the screen, then click Settings. The Settings window opens.
3. **Open Personalization.** (Settings > Personalization) In the Settings window, click Personalization. This is the section that holds custom instructions.
4. **Open Customize ChatGPT.** (Personalization > Customize ChatGPT) Click Customize ChatGPT. Some versions label this Custom instructions, so use that label if it is the one you see.
5. **Fill in the first field.** Type what ChatGPT should know about you. Keep it to facts that change its answers, such as your job, your tools and your skill level. Stay under the character limit for your plan.
6. **Fill in the second field.** Describe how you want answers shaped: length, format, tone and anything to avoid. Short, direct rules work better than long lists of hopes.
7. **Turn on Enable for new chats.** If your screen shows an Enable for new chats toggle, make sure it is switched on. Without it, your text may sit there without changing new chats. Tip: TechSnaply's May 2026 guide says to check that both fields contain text as well.
8. **Save and close Settings.** Click Save if the window shows that button, then close Settings. Reopen the window and confirm the text is still in both fields.
9. **Test in a new chat.** Start a new chat. Ask for something where your instructions should show, such as a summary in your preferred format. Compare the reply with the rules you wrote.
10. **New desktop app: open Settings.** (ChatGPT > Settings) Shortcut: ⌘ ,. In the new ChatGPT desktop app, press ⌘, or open Settings from the app menu. Look under Personalization for memory options, such as Enable Codex memories, where that option is available.
11. **New desktop app: find AGENTS.md.** OpenAI's docs say personal instructions are stored in AGENTS.md on the selected machine, and you edit them there. The docs give no full file path, so look in Settings first before you search your disk.

Custom instructions tell ChatGPT who you are and how you want it to answer. You write them once, and ChatGPT applies them to new conversations. That saves you from retyping the same background in every chat. This page covers the Mac, where the app names and screens changed in 2026. It shows the path in the older app, the path in the new desktop app, and what to do when your instructions seem to be ignored.

## Which ChatGPT app you have on your Mac

On July 9, 2026, OpenAI renamed the original Mac app ChatGPT Classic. A new ChatGPT desktop app combined Codex into one product. According to 9to5Mac, the way forward is the new app. The two apps can be installed side by side. Classic looks more native to the Mac, which may matter to some people. 9to5Mac gives no version numbers for either app, so the app name is your safest guide.

- Open Finder, then Applications, and look for ChatGPT Classic and ChatGPT.
- Open the app you plan to use. If its menu bar and Settings look different from the steps below, you may have the other app.
- Follow only the path that matches the app you open. Skip the steps for the other app.

## Set custom instructions in ChatGPT Classic

The Classic path matches most older guides. iGeeksBlog, last updated in January 2026, says to open ChatGPT, then Settings, then Personalization, then Customize ChatGPT. The Mac Install Guide lists the same path as Application menu, Settings, Personalization, Customize ChatGPT. It also says the instructions are shared with the web browser version of ChatGPT. Text you save on the Mac is the same text you see in your browser.

![Person at a desk typing on a Mac laptop while setting up how to set custom instructions in ChatGPT](https://images.lazur.app/content-images/howto/set-custom-instructions-in-chatgpt/how-to-set-custom-instructions-in-chatgpt-1-20a219.jpg)

Some screens label this section Custom instructions instead of Customize ChatGPT. A May 2026 TechSnaply post uses that wording. It describes two fields, a check that both contain text, and a toggle called Enable for new chats. If you see either label, you are in the right place.

## What to write in the two fields

The fields are short, so spend your words on facts that change the answer. Say what you do and what you already know. Then say how you want answers shaped. Skip anything ChatGPT would guess anyway, such as a request to be polite. A good test is whether a new colleague would need the sentence to do the job well.

| Field | What to put there | Example |
| --- | --- | --- |
| What ChatGPT should know about you | Your job, your tools and your skill level | I work in Excel and SQL every day and I know both well. |
| How ChatGPT should respond | Length, format, tone and what to avoid | Keep answers short. Use bullet points. Skip apologies and summaries. |
| Context you keep retyping | Facts that repeat in most of your chats | I write for a general audience in plain English. |

_Example entries for each part of the two custom instruction fields._

## Write instructions that hold up

Short and specific beats long and vague. Be helpful tells ChatGPT almost nothing, because every answer is meant to help. A rule like show the full formula, then explain only the cells that changed tells it exactly what you want. Write rules you would give a new colleague on their first day. Then test them in a new chat and tighten the wording if the replies drift.

- Analyst: I work in Excel and SQL and know both well. Skip basics. Put formulas in code blocks.
- Newsletter writer: I write for a general audience in plain English. Give a few headline options when I ask. Keep sentences short.
- Student: I am studying biology for an exam. Explain ideas step by step. Ask one question before you give a final answer.

## Character limits: 1,500 or 5,000 characters

The limit depends on your plan. LaunchReady reports that Free and Go accounts can save up to 1,500 characters of custom instructions. It says Plus, Pro, Business, Enterprise and Education accounts can save up to 5,000. The article ties the change to mid-July 2026 and cites OpenAI's Help Center, but it gives no exact date.

Treat those figures as reported, not confirmed. At the time of writing, OpenAI's own help pages could not be checked. A May 2026 TechSnaply post still says each field is limited to 1,500 characters, which conflicts with the paid figure. If your text is too long, trim it before you save. Count the characters in a text editor first.

- **44%** of U.S. adults say they use ChatGPT, up from 34% in 2025 (February 2026 survey) ([source](https://www.pewresearch.org/internet/2026/06/17/americans-and-ai-2026-chatbots-smart-devices-and-views-on-impact/))
- **1,500** characters of custom instructions on Free and Go accounts ([source](https://launchready.ai/insights/ai-readiness/chatgpt-custom-instructions-5000-characters-owner-playbook))
- **5,000** characters on paid plans, a limit reported in mid-July 2026 ([source](https://launchready.ai/insights/ai-readiness/chatgpt-custom-instructions-5000-characters-owner-playbook))

## Test that the instructions apply

Start a new chat after you save, because instructions apply to new conversations. Ask for something where the rules should show. A short summary in a fixed format works well. Compare the reply with what you wrote, and do not judge from one answer alone.

Say your profile says you are a data analyst who works in Excel. Your second field asks for short answers with bullet points. Start a new chat and ask for a summary of a sales table. If the reply comes back as bullet points with no greeting, the instructions are working. If it comes back as a long essay, check the toggle and the fields, then try again in a new chat.

## Why the quick chat bar may ignore them

iGeeksBlog says the chat bar does not support these settings. That is easy to miss, because the chat bar looks like the rest of ChatGPT. Open a full chat window when you test. Use the chat bar for quick questions where your instructions do not matter.

## Option+Space and the ChatGPT launcher

On Mac, Option+Space opens the ChatGPT launcher. The app must be running for the shortcut to work. The Mac Install Guide says you can change the shortcut in Settings. For more detail, read [How to use the Option+Space shortcut in ChatGPT on Mac](https://www.lazur.app/how-to/use-the-option-space-shortcut-in-chatgpt).

![Man working on a Mac at a desk, reviewing ChatGPT settings for how to set custom instructions](https://images.lazur.app/content-images/howto/set-custom-instructions-in-chatgpt/how-to-set-custom-instructions-in-chatgpt-2-7f90a8.jpg)

## The new ChatGPT desktop app and AGENTS.md

The new app works differently. OpenAI's documentation for the ChatGPT desktop app, which it also calls Codex, says Settings opens from the app menu or with ⌘,. Under Personalization, you can turn on Enable Codex memories where that option exists. That toggle controls memories, not the text of your instructions.

The same docs say personal instructions are stored in AGENTS.md for the selected machine, and you edit them there. They give no full file path and no version number. So search in Settings first, then look for the file if you still need it. Keep the text plain and short, and save it before you open a new chat.

## When new chats ignore your instructions

A May 2026 TechSnaply post lists fixes, roughly from the cheapest to the most involved. Start with the toggle. Switch Enable for new chats off, then on, and save. Move to the next fix only when the first one fails. The troubleshooting list below follows the same order.

## Common mistakes to avoid

- Pasting a whole document. Long pasted text eats the limit and buries the rules that matter.
- Writing a task for today. Instructions apply to every new chat, so a one-off task belongs in that chat.
- Forgetting the toggle. If Enable for new chats is off, the text sits there and does not apply to new chats.
- Testing in the quick chat bar. iGeeksBlog says the chat bar does not support these settings.
- Assuming the Mac and web versions differ. The Mac Install Guide says they share the same instructions.
- Ignoring your plan limit. Free and Go accounts have less room than paid plans.

## Requirements and menu paths at a glance

| Item | What to expect |
| --- | --- |
| Chip | Apple silicon, M1 or newer. The Mac app is not available for Intel Macs. |
| macOS | macOS 14 Sonoma or later. |
| Classic settings path | ChatGPT > Settings > Personalization > Customize ChatGPT |
| New app settings | Settings from the app menu, or with ⌘, |
| New app storage | Personal instructions kept in AGENTS.md on the selected machine |

_Requirements and settings paths from the sources used on this page._

## How to edit or turn off custom instructions

To change instructions, open the same screen, edit the text, and save. To stop them from applying, switch off Enable for new chats if your screen shows that toggle. Clearing both fields also removes them, according to TechSnaply. Save again, then start a new chat so you can confirm the change took.

## What to do next

Use the instructions for a few days of normal work before you change them again. Change one line at a time, so you can see which edit made the difference. When you need to share a document in a chat, follow [How to attach a file in ChatGPT on Mac](https://www.lazur.app/how-to/attach-a-file-in-chatgpt).

## Shortcuts

- Open Settings in the new ChatGPT desktop app: ⌘ ,
- Open the ChatGPT launcher, with the app running: ⌥ Space
- Start a Temporary Chat in ChatGPT Classic: ⇧ ⌘ N

## If it does not work

- **Instructions do not apply to new chats** Switch Enable for new chats off, then on, and save. If that fails, clear both fields, save, paste the text back and save again. Then sign out, clear the browser cache and test in an incognito window with extensions off.
- **Text will not save or gets cut off** Check your plan limit. LaunchReady reports 1,500 characters for Free and Go accounts and 5,000 for paid plans. Trim the text, then save again.
- **I cannot find Customize ChatGPT** Look for Custom instructions instead, since guides use both labels. Check the app name too. In the new desktop app, the instructions are stored in AGENTS.md, so follow the new app steps.
- **The Mac app and the web version show different instructions** The Mac Install Guide says the instructions are shared with the web version. Reload the page or restart the app, then check the text again.
- **The app will not install on my Mac** The Mac app needs an Apple silicon chip, M1 or newer, and macOS 14 Sonoma or later. It is not available for Intel Macs, so use ChatGPT in a browser on those machines.
- **The quick chat ignores my instructions** iGeeksBlog says the chat bar does not support these settings. Open a full chat window and test there.

## With Lazur

Lazur is a voice assistant for the Mac that lives in the notch. Hold ⌥ ⌘ and ask; it sees your screen, answers out loud, points at buttons and walks you through apps. Hold fn to dictate. Free for 3 days, then $18/month: https://www.lazur.app/download

- “Walk me through setting custom instructions in ChatGPT.”: Lazur guides you one click at a time and waits for each click before it names the next one. (Walks you through it)

## FAQ

### Do custom instructions in ChatGPT on Mac also work on the web?

Yes, according to the Mac Install Guide. It says the instructions are shared with the web browser version of ChatGPT, so you only set them once.

### Is there a keyboard shortcut for custom instructions?

No source I checked lists one. iGeeksBlog gives no shortcut for them. In the new desktop app, ⌘, opens Settings, which is the closest route.

### Why can't I find Customize ChatGPT?

Some screens say Custom instructions instead. The new desktop app stores personal instructions in AGENTS.md, so check which app you have first, then look under Settings and Personalization.

### How many characters can I use in custom instructions?

Free and Go accounts can save up to 1,500 characters. LaunchReady reports that Plus, Pro, Business, Enterprise and Education accounts can save up to 5,000, a change it dates to mid-July 2026.

### Can I use custom instructions on an Intel Mac?

Not in the Mac app. It needs an Apple silicon chip, M1 or newer, and macOS 14 Sonoma or later. On an Intel Mac, use ChatGPT in a browser instead.

### Do custom instructions work in the quick chat bar?

iGeeksBlog says the chat bar does not support these settings. Start a full chat window when you need the instructions to shape the answer.

### Should I put my whole project brief in custom instructions?

Usually not. Instructions apply to every new chat, so project details work better inside that chat. Keep the instructions for lasting facts about you and how you like answers.

### Does the 44% Pew figure mean most people use custom instructions?

No. Pew reports that 44% of U.S. adults say they use ChatGPT. It says the 2026 question also asked about other chatbots, so the trend is not exactly comparable with earlier years. It says nothing about custom instructions.

## Sources

1. [How to Use ChatGPT App on Mac: A Step-By-Step Guide](https://www.igeeksblog.com/how-to-use-chatgpt-on-mac/), iGeeksBlog, checked 2026-11-09
2. [ChatGPT for Mac (Mac Install Guide)](https://mac.install.guide/ai/chatgpt-desktop), Mac Install Guide, checked 2026-11-09
3. [OpenAI unveils ChatGPT Work agent, GPT-5.6 models now available](https://9to5mac.com/2026/07/09/openai-announcing-the-next-chapter-for-chatgpt-today-watch-here/), 9to5Mac, checked 2026-11-09
4. [Settings (ChatGPT desktop app docs)](https://learn.chatgpt.com/docs/app/settings), OpenAI, checked 2026-11-09
5. [ChatGPT Custom Instructions Now Hold 5,000 Characters](https://launchready.ai/insights/ai-readiness/chatgpt-custom-instructions-5000-characters-owner-playbook), LaunchReady, checked 2026-11-09
6. [ChatGPT Custom Instructions Not Applying to New Chats](https://techsnaply.bokgoon.com/2026/05/chatgpt-custom-instructions-not.html), TechSnaply, checked 2026-11-09
7. [Americans' Views on AI Chatbots, Smart Devices and AI's Impact](https://www.pewresearch.org/internet/2026/06/17/americans-and-ai-2026-chatbots-smart-devices-and-views-on-impact/), Pew Research Center, checked 2026-11-09