AI Guides
System prompts and custom instructions
Configure lasting guidance so everyday prompts stay shorter.
Guide notice
Guides provide decision frameworks and topic overviews. They link to related comparisons, tools, pricing, and benchmarks so you can verify details in context.
Editorial status
Published 2026-07-30 · Last reviewed 2026-07-30 · Next review due 2027-01-26
- Review cadence: Every 6 months
- Verification badge: Verified
- Review status: Current
- Evidence level: editorial
- Content owner: ONULSURI Editorial
Introduction
System prompts and custom instructions define standing rules: role, tone, formatting defaults, and what the assistant should refuse or escalate. Task prompts then focus on the specific job.
Keep standing instructions short, test them against real work, and avoid stuffing unique project details that change weekly.
Standing rules that conflict with everyday task prompts create silent failures. Version instructions like policy text, never store secrets in synced custom instructions, and resolve conflicts in one owned document.
Who it is for
- Power users configuring ChatGPT, Claude, or Copilot preferences.
- Teams aligning assistant behavior across people.
- Builders designing product-level system prompts.
- Admins standardizing workspace-level assistant behavior.
Decision framework
- Capture only durable rules
Put stable preferences and safety constraints in system instructions.
- Leave task details in user prompts
Project-specific facts belong in the request or retrieved context.
- Test conflicting instructions
Check what happens when a task prompt contradicts standing rules.
- Version and review
Treat system prompts like policy text with an owner and review date.
- Ban secrets from standing instructions
Custom instructions sync with accounts. Keep credentials and regulated data out of them entirely.
Comparison overview
System vs user prompt
System instructions persist; user prompts are job-specific.
Personalization vs policy
Tone preferences differ from compliance requirements—label both clearly.
Length trade-off
Long system prompts consume context and can dilute important rules.
Common mistake to avoid
Stuffing an essay of conflicting rules into custom instructions, then blaming the model for inconsistency.
Related AI tools
Related compare pages
Related pricing pages
Related benchmarks
Related prompt categories
FAQ
What belongs in custom instructions?
Durable preferences such as role, tone, formatting defaults, and standing constraints.
Can system prompts replace review?
No. They shape behavior but do not guarantee correctness.
How long should they be?
Short enough to stay memorable and testable—prefer a tight checklist over a manifesto.
Should every teammate share one system prompt?
Share core policy rules; allow personal tone preferences where appropriate.
Are custom instructions private?
They are stored by the product account. Follow your organization's data rules — do not place credentials or regulated data there.
Further reading
- Prompt engineering basics — Complement standing rules with task prompts.
- Prompt libraries for teams — Operationalize shared instructions.
- AI ethics practical guide — Include ethical constraints thoughtfully.
- Email prompts — Apply instructions to email tasks.
Related hubs
- AI Hub — Overview of ONULSURI AI guides and where each section fits.
- AI Compare — Side-by-side comparisons of assistants and tools.
- AI Tool Directory — Category directory and tool overviews.
- AI Pricing — Plan structure and upgrade guidance without fabricated prices.
- AI Benchmarks — Transparent evaluation frameworks and scenario suites.
- Prompt Library — Reusable prompts for coding, writing, and everyday work.