System Prompt Builder 🤖 ✨
Compose clear system messages for ChatGPT, Claude, and other LLMs. Choose a preset, define identity and boundaries, then copy or download. No sign-up required.
Presets fill fields when they still match the previous preset defaults (merge-if-unchanged). Custom keeps your text.
Advanced options
Add a non-empty identity or role to enable Copy and Download.
About this system prompt builder
A strong system prompt defines who the assistant is (identity), what it can do (capabilities), what it must not do (boundaries), how it should sound (tone), how to format answers (output rules), how to use conversation context, and when to refuse (safety). Optional examples show the desired interaction style. Multi-line capability, boundary, and safety fields become bullet lists in the assembled prompt.
Presets such as Coding assistant, Tutor, or Support agent pre-fill these sections. Switching presets uses merge-if-unchanged so your edits survive when they no longer match the old template defaults. Everything is processed only in your browser.
Frequently asked questions
Does this tool send my text to a server or an AI?
No. Everything runs in your browser. Your fields are assembled into one system prompt on your device; nothing is sent to our servers for generation.
What is the difference between a system prompt and a user prompt?
A system prompt sets persistent behavior, boundaries, and tone for the assistant. User prompts are the per-turn requests. Use this tool for the system side; pair it with our Prompt Generator for user messages.
What does merge-if-unchanged mean?
When you change the preset, fields update only if they still match the previous preset defaults (or are empty). If you edited them, your text is kept—unless you chose Custom, which never overwrites your text.
Why is Copy disabled?
Add a non-empty identity or role first. The tool needs a core persona before it can build a system prompt worth copying.
Can I save without using the clipboard?
Yes. Use Download .txt to save the assembled system prompt as a plain text file.