System prompt builder
Assemble a system prompt from role, rules, and output format sections.
Runs in this tab. The file stays here.
This runs in your browser. Nothing is uploaded.
About System prompt builder
Fill in role, context, task, rules, output format, and examples, and get a structured system prompt in Markdown sections or XML tags. Built in your browser.
Most system prompts end up with the same parts: who the assistant is, what it needs to know, what it's being asked to do, the rules it must follow, what the answer should look like, and a couple of examples. The form has a box for each. Type in them, and the assembled prompt on the right updates as you go. Rules go one per line, and each becomes a bullet; any leading dash or number you paste in is cleaned off.
The style switch matters more than it looks. In Markdown mode the role comes first as plain text and every other part gets a heading such as "Rules" or "Output format". In XML mode each part is wrapped in its own tag, such as <rules> or <output_format>, which some people find makes the sections harder for a model to confuse with the content that follows. Neither style is magic. Try both on your own task and look at the results.
Empty boxes are left out completely, so a short prompt stays short. The page starts with a sample role and two sample rules to show the format; delete them if you don't want them. It doesn't send the prompt anywhere, run it against a model, or judge whether it's any good. It organises what you write, nothing more, so the quality of the output is the quality of the input.
How to use System prompt builder
- 1Write the role, then fill in only the sections you need.
- 2Put one rule per line.
- 3Choose Markdown sections or XML tags.
- 4Copy the finished prompt.
What it won't do
- Fixed sections: role, context, task, rules, output format, examples.
- Structures text only; no testing, scoring, or model calls.
- Nothing is saved between visits.
Common questions
Does it send my prompt to a model?
No. It assembles text in your browser. You paste the result into the playground, SDK call, or settings page you use.
Markdown or XML tags: which is better?
There's no universal answer. Tags give clear boundaries around things like examples or pasted documents; Markdown reads more naturally to humans. The builder makes it a single click to switch, so compare them on your actual task.
Why is a section missing from the output?
Empty boxes are skipped. Fill the box in and the section appears.
Related tools
Why this one doesn't upload your file
There is no server to upload to. This page is a static file, and the work happens in your browser using the same graphics and WebAssembly code that renders every other site you visit. Your file is read from disk into memory, processed, and handed back as a download. Once the page has loaded you can disconnect from the network entirely and it keeps working. The longer explanation