Guide
ChatGPT custom instructions character limit: what to do when you hit it
OpenAI's help page gives ChatGPT custom instructions a limit of 1,500 characters on Free and Go and 5,000 on Plus, Pro, Business, Enterprise and Edu (read through search-result text on 5 November 2026), though what Settings > Personalization lets you save is the final word. If you keep hitting it, the box is holding things it shouldn't: custom instructions are for preferences that apply to every chat, such as your role, the format you like and the words you avoid. Move one client's or project's background into that project's instructions and files, and a task you repeat, with its steps and examples, into a skill that's used only when that task comes up. What's left usually fits in a few hundred characters.
Short answer
- The limit: 1,500 characters on Free and Go, 5,000 on Plus and above.
- Stays: role, tone, format, what to avoid.
- To a project: one client's or project's background.
- To a skill: a repeated task's steps and examples.
Where each kind of line goes
| Line in your instructions | Where it goes | Why |
|---|---|---|
| Your role, tone, preferred format | Custom instructions | Applies to every chat |
| A client's background, a project's facts | That project's instructions and files | Needed only in that project's chats |
| A policy or price list | A file the project reads | One current copy; instructions point to it |
| Steps and examples for one repeated task | A skill | Used when that task comes up, and shareable |
| "Be helpful", "be accurate" | Delete | The AI does it anyway |
The brief to copy
Trim my custom instructions
"Here are my custom instructions: [paste]. Sort every line into one of four groups: Stays (applies to every chat), Project (background for one client or project), Skill (steps or examples for one task I repeat), Delete (generic, or never fixed a real problem).
Then rewrite what stays, most important first: my role and goal in 2 sentences, tone with one example phrase, what not to do with what to do instead, where the facts live (point to the project; don't paste them), and the format of a good answer. Keep it under [limit] characters and show the count."
A worked example
Illustration: a made-up business. The HR manager of a 90-person logistics company, on ChatGPT Plus, has 4,800 characters of custom instructions: her role (300), tone (250), a summary of the leave policy (1,600), a job post template (1,500), interview rules (700) and a list of managers and teams (450). The leave summary and the manager list move to her HR project's files, and the job post template and interview rules become two skills. What stays, at 476 characters:
Custom instructions after the trim
Role and goal: I'm the HR manager at a 90-person logistics company. Help me draft HR documents and replies that match our policies and are ready to send.
Tone: plain and warm, short sentences. For example: "Here's what changes for you on 1 April."
Don't quote a policy from memory: ask me to open the HR project, which has the current policies. Don't give legal advice: mark it [check: counsel].
Format: the draft first, then a line "Check:" listing anything I should confirm.
The old instructions quoted last year's leave policy in every chat, including chats that had nothing to do with leave. Now the policy lives in one file she updates in April, and the job post skill loads only when she asks for a job post.
Next step: the same setup for the whole team
Once your own instructions are short, the project and the skills are what your colleagues need too. How to get your team to use AI the same way covers sharing them so everyone works from the same version.
Skills for this
- AI practiceContext brief for an AI assistantWrites instructions for an AI assistant or agent: role, audience, can and can't, sources of truth, tools, format, examples, edge cases, and handoff.
- AI practiceTurn a prompt into a skillTurns a prompt that works into a skill the whole team can reuse, with a valid name, a when-to-use description, steps, an output template, an example, and checks.
- MarketingBrand voice guide and rewriteExtracts a voice guide from 3 to 5 sample texts (traits with do and don't pairs, a word list, mechanics) and rewrites a draft in it.
Questions
What is the character limit for ChatGPT custom instructions?
OpenAI's help page on custom instructions, read through search-result text on 5 November 2026, gives 1,500 characters on Free and Go and 5,000 on Plus, Pro, Business, Enterprise and Edu. Limits change, so go by what Settings > Personalization lets you save, not by any page, this one included.
What do I do when my custom instructions are too long?
Sort every line by where it belongs. What applies to every chat stays: your role, tone, format and the mistakes to avoid. Background for one client or project moves to that project's instructions and files. A task you repeat, with its steps and examples, becomes a skill. Lines that never fixed a real problem go.
Do projects have their own instructions?
Yes. In ChatGPT, a project's instructions apply across that project's chats, next to its files. In Claude, Instructions for Claude in Settings apply across your account, and each project's instructions apply only to chats in that project. That's why background for one client belongs in a project and not in instructions every chat reads.
AI skill
Have your AI write the instructions for your AI assistant
Put this skill in AI Skill Pod and everyone on your team gets it in their Claude, Cursor or ChatGPT (Pro, Business, Enterprise): one invite link, free to start. Context brief for an AI assistant has your AI rewrite long instructions into a short brief: the role and goal in two sentences, tone with an example phrase, what not to do and what to do instead, where the facts live instead of the facts themselves, and the format of a good answer, most important first.
14 days free · No card needed
Sources
- OpenAI Help: ChatGPT custom instructions — Free and Go users can save up to 1,500 characters in custom instructions; Plus, Pro, Enterprise, Business and Education users up to 5,000; read through search-result text, the page blocks automated reads (read 2026-11-05)
- OpenAI Help: ChatGPT release notes — 15 July 2026, "Increased custom instructions limit": OpenAI is increasing the character limit for custom instructions; read through search-result text (read 2026-11-05)
- ChatGPT docs: Projects and chats — project instructions apply across the project's chats; a project keeps related chats, files, instructions and sources together (read 2026-11-05)
- Claude Help Center: Understanding Claude's personalization features — Instructions for Claude (Settings > Your Claude) are account-wide; project instructions "only apply to chats within that project" (read 2026-11-05)
- Anthropic: Effective context engineering for AI agents — "the smallest set of high-signal tokens that maximize the likelihood of your desired outcome" (read 2026-11-05)