ChatGPTProjectsLevel 2: Context

How Do ChatGPT Project Instructions Work?

They're standing rules for one project. Add them from the more options menu (•••) under Project settings. OpenAI's help page says they apply only within that project and override your global custom instructions.

Prompt to copy 
Paste this into Project settings, then fill it in:

Role: You are helping with [work] for [client or audience].
Voice: [tone, spelling, words to use or avoid].
Format: Unless I ask otherwise, answer as [structure and length].
Sources: Use the project files first. Say which file you used. If the files don't cover something, say so before answering from general knowledge.
Always: [1 to 3 rules that apply to every chat].
Never: [1 to 3 things that have gone wrong before].
  1. 1Global custom instructionsAll your chats
  2. 2Project instructionsOverride global, in this project only
  3. 3Every chat in the projectChats moved in later inherit them
Inside a project, project instructions override your global ones. Outside it, they do nothing. From OpenAI's help page.

Try it now

  1. 1Open your project and select the more options menu (•••), then Project settings.
  2. 2Add three lines: one for voice, one for format and one rule you keep repeating.
  3. 3Save, then start a new chat there and give it a short request without mentioning any of those rules.
  4. 4It worked if the answer follows all three. Then open a chat outside the project and confirm the rules don't apply there.

Use it when

When one body of work needs its own voice, format or rules: a client with a house style, a course with a citation format, a report with a fixed structure. If you keep typing the same "remember to..." line in that project's chats, move it into the instructions.

Skip it when

For rules you want everywhere, like how long answers should be. Those belong in global custom instructions, which hold up to 1,500 characters on Free and Go and 5,000 on Plus, Pro and business plans. Don't use them for a one-chat request either. A line in your message is enough.

Why it works

Your global custom instructions apply to all chats, so they can't hold one client's voice without affecting everything else. Project instructions solve that by staying inside one project. OpenAI's docs say they apply across a project's chats. A chat you move in later inherits them too. On Enterprise and Edu, OpenAI's table shows global custom instructions aren't available inside projects at all, so project instructions are the only ones in play.

Example

Say you manage two clients. Project "Harlow Legal" gets: "Formal, British English, no contractions, cite the policy number when one's given." Project "Sunny Pet Co" gets: "Friendly, American English, short sentences." You ask both for the same out-of-office reply, and each one should follow its own rules. Neither project's rules reach your chats outside it.

Going further

Instructions aren't private in a shared project. OpenAI says members with edit access can update instructions, and members with chat access can see them. A shared project also uses project-only memory, so it can't use members' personal custom instructions or memories, which means a colleague gets the project's rules and not yours. The help pages read for this card give a character limit for global custom instructions but none for project instructions, so keep them short and test them. Rule of thumb, not an OpenAI figure: if a line never changes an answer, cut it.

Common mistakes

  • Writing only what differs from your global rules. OpenAI says project instructions override global ones, but its pages don't say whether global rules that don't conflict still apply on personal plans. Put every rule the project needs in the project.
  • Expecting your global rules to carry into a shared project. They won't reach your teammates, so write out the rules the project needs.
  • Telling ChatGPT in a chat to "always do this from now on" and expecting it to change the project. Edit Project settings, since a message isn't the same as an instruction.
  • Letting anyone with edit access rewrite the rules with no warning. Give most people chat access if the voice matters.

Sources

Checked 6 November 2026. Products change often, so confirm details with the vendor.

Related

Technique How Do You Set Up a ChatGPT Project? Best practice How Do You Set Up ChatGPT Custom Instructions? Mistake Should You Use One ChatGPT Project or Several? Concept How Do You Prompt ChatGPT's Reasoning Models?

Beyond the course

Glossary Model Context Protocol (MCP) Pricing guide ChatGPT pricing, plans and models