Is token count exact?

Prompt preview uses a quick estimate for planning; final model counts may vary.

Can I use this with any model?

Yes. Prompts are plain text and can be adapted to different providers.

System Prompt Builder

Runs in browser

Build reusable LLM system prompts from structured templates.

Build robust system prompts from structured sections and role templates. Preview assembled output with character and approximate token count.

TemplateAdvanced mode

Role & Persona

Primary Goal

Instructions

Constraints

Output Format

Live preview

Role & Persona:
You are an expert software engineer with strong TypeScript, React, and system design experience.

Primary Goal:
Help developers write clean, efficient, and maintainable code.

Instructions:
- Explain reasoning briefly.
- Prefer safe defaults.
- Include concrete code when useful.

Constraints:
- Never invent APIs.
- Do not leak secrets.
- Ask clarifying questions when requirements are ambiguous.

Output Format:
Use concise markdown with sections: Solution, Code, Notes.

488 characters · ~122 tokens (approx)

🔒 Runs in your browser · No uploads · Your data never leaves your device

How to use

Select template
Start from Custom, Coding Assistant, Customer Support, and other presets.
Fill sections
Edit role, goal, instructions, constraints, output format, and examples.
Copy preview
Use live assembled prompt output directly in your LLM app or SDK.

Common use cases

Building consistent AI personas — Define a role, objective, and output format once and reuse the system prompt across all API calls.
Standardizing prompts across a team — Generate a structured prompt template that your team follows for consistent LLM behavior.

Examples

Coding assistant
Template-first workflow.
Output
```
Role + Goal + Rules + Output format...
```

Frequently asked questions

Is token count exact?: Prompt preview uses a quick estimate for planning; final model counts may vary.
Can I use this with any model?: Yes. Prompts are plain text and can be adapted to different providers.

Key concepts

System prompt: An instruction given to an LLM at the start of a conversation that sets its role, tone, and behavior throughout the session.
Role prompt: A system prompt that assigns a specific persona or expertise to the model (e.g., 'You are a senior code reviewer').

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