Prompt Template Renderer Online — Free & Private

Free, no signup, runs entirely in your browser — your data never leaves your device.

Usage

# Simple substitution
curl "https://prompt-template-renderer-formatho.filesformatho.workers.dev/api?template=Hello%20%7B%7Bname%7D%7D%2C%20welcome%20to%20%7B%7Bproduct%7D%7D!&vars=%7B%22name%22%3A%22Ada%22%2C%22product%22%3A%22Formatho%22%7D"

# Nested variables with dot paths
curl "https://prompt-template-renderer-formatho.filesformatho.workers.dev/api?template=%7B%7Buser.name%7D%7D%20(%7B%7Buser.role%7D%7D)%20filed%20%7B%7Bticket.count%7D%7D%20issues&vars=%7B%22user%22%3A%7B%22name%22%3A%22Grace%22%2C%22role%22%3A%22admin%22%7D%2C%22ticket%22%3A%7B%22count%22%3A7%7D%7D"

# Fail loudly on missing variables
curl "https://prompt-template-renderer-formatho.filesformatho.workers.dev/api?template=Hi%20%7B%7Bname%7D%7D&vars=%7B%7D&missing=error"

Returns the rendered template plus variables_used, variables_missing and variables_unused lists — handy for auditing prompt templates before they reach an LLM. Missing variables can be kept as-is (default), replaced with an empty string, or raise a 400 error naming every gap. Values may be strings, numbers, booleans, null or nested objects (objects render as JSON).

Full parameter reference: /api endpoint.

Full browser tool

Render templates entirely client-side: Prompt Template Renderer on formatho.com.

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