System Prompt & Custom Instructions Generator
Craft elite system instructions, Cursor rules, and ChatGPT/Claude custom prompts with role constraints and anti-hallucination guardrails.
System Prompt & Custom Instructions Generator
Build production-grade system prompts, ChatGPT custom instructions, guardrails, tone, and formatting rules for LLMs.
[ROLE] You are an elite Principal Software Engineer and System Architect. You prioritize clean code, idiomatic modern standards, security, strict typing, and high-performance algorithms. [COMMUNICATION STYLE] Be extremely concise. Get directly to the answer without introductory pleasantries, conversational filler, or meta-commentary. [HOW YOU SHOULD RESPOND] • Always use clean GitHub Flavored Markdown (headers, bulleted lists, inline code backticks, tables). • Do not say "Sure!", "Here is your code", or "I hope this helps". Output only the requested solution. • Never provide incomplete snippets with placeholder comments like "// do something here". Provide complete, runnable code. [RULES & CONSTRAINTS] • If a fact, API parameter, or library does not exist or you are uncertain, explicitly state so instead of guessing. • Never apologize for mistakes or limitations. Simply acknowledge the correction and supply the updated answer immediately.
- For ChatGPT: Paste into Settings > Custom Instructions.
- For APIs: Pass directly into the "system" parameter or Claude system box.
Overview
Free online system prompt and custom instructions generator. Build production-grade prompts with role personas, negative constraints, output formatting schemas, and target-specific configs for ChatGPT, Claude, OpenAI API, and Cursor .cursorrules.
System Prompt & Custom Instructions Generator Guide
System prompts and custom instructions are the foundational directives that dictate how LLMs behave, reason, and structure their answers.
By framing identity, audience tone, constraints, and negative examples upfront, you minimize hallucinations and avoid repetitive prompt phrasing.
This tool compiles ready-to-use system directives for ChatGPT, Claude 3.5, OpenAI API, and Cursor .cursorrules files.
How to Build an Elite System Prompt
Fast & IntuitiveSelect Target & Persona
Choose ChatGPT, Claude, API, or Cursor and define the model persona.
Configure Tone & Formatting
Set tone preferences, response length limits, and structured format guidelines.
Apply Guardrails & Copy
Activate anti-hallucination constraints and copy your production-ready system prompt.
Key Highlights & Advantages
Zero server uploads. Everything processes securely within your local browser memory.
Immediate results with no file upload or download queues.
No registration, no paywalls, and no hidden quotas.
Seamlessly optimized for mobile smartphones, tablets, and desktop workstations.
All data processing runs natively via W3C compliant browser hardware acceleration.
- Explicitly instructing the model to show intermediate reasoning steps improves code and mathematical accuracy.
- Use XML tags like <rules> and <output_format> when targeting Claude 3.5 models.
Frequently Asked Questions
2 Q&AsWhat is the difference between system and user prompts?
System prompts establish persistent identity and meta-rules; user prompts provide specific tasks for a single turn.
How do I use this in Cursor?
Create a .cursorrules file in the root of your repository and paste the generated instructions.

