What placeholder syntax does it support?

It matches double-brace placeholders such as the {{variable}} style used by Mustache, Handlebars, and most prompt frameworks. Variable names may contain letters, numbers, underscores, dots, and hyphens.

Why does an undefined variable matter?

A variable used in the template with no provided value will render as a literal placeholder or an empty string at runtime, silently corrupting the prompt the model receives. The checker turns that into a visible error.

What is an unused variable?

It is a value you defined that the template never references. It is usually harmless but often signals a typo in the variable name or leftover state from an earlier version, so it is flagged as a warning.

Does it detect typos in braces?

Yes. It warns when it finds stray single or unmatched braces that do not form a valid placeholder, which is a common cause of placeholders that never get substituted.

Does my template leave the browser?

No. All parsing and checking runs locally in JavaScript. Nothing is uploaded or stored.

Prompt Variable Scope Checker

Prompt variable scope checker

Templated prompts are powerful and fragile. Misspell a placeholder name or forget to supply a value, and the variable renders as raw text or an empty string — the model gets a broken prompt and you get mysterious bad outputs. This checker treats a prompt template like code: it cross-references every {{variable}} against the values you supply and flags anything that does not line up.

How it works

You paste a template using double-brace placeholders and a list of the variables you actually provide, written as key = value lines. The tool extracts every placeholder from the template and every key from your definitions, then computes two sets: variables used in the template but never defined (reported as errors, because they will render empty), and variables defined but never used (reported as warnings, usually a typo or leftover). It also warns about stray braces that do not form a valid placeholder.

Tips and notes

Run it before every prompt change. The most common production bug is a renamed variable that one side forgot to update.
Unused warnings catch typos. If {{audience}} is flagged unused but you expected it, check whether the template says {{audiance}}.
Empty is silent. An undefined variable rarely throws — it just degrades output quality, which is why catching it statically matters.
Everything is local. No upload, so it is safe to paste proprietary templates.