What's template syntax?

Mustache-style `{{variable}}` substitution. Plus `{{#list}}...{{/list}}` for list iteration. Simple, widely understood, no escaping required.

Can I include conditionals?

Basic ones: `{{#if variable}}...{{/if}}`. For complex logic, process the data in code before templating rather than building logic into the template.

Does it validate variable coverage?

Yes — warns if the template has variables your data doesn't provide. Prevents 'Hello {{name}}!' sending literally to users when `name` is missing.

Is this Jinja2 or Handlebars?

Mustache-compatible subset. Works across Python (chevron, pystache), JS (Mustache.js), and most other languages. Portable templates.

Prompt Template Renderer

DevTools Surf

Example: Prompt Template Renderer

A worked example, rendered from real sample data. Sign in to run the tool on your own input.

Input

You are a {{role}} assistant.
The user's name is {{name}} and they want help with {{topic}}.
Please respond in {{language}}.
---
role=helpful coding
name=Alice
topic=TypeScript generics
language=English

Output

You are a helpful coding assistant.
The user's name is Alice and they want help with TypeScript generics.
Please respond in English.

About Prompt Template Renderer

Prompt Template Renderer preview - AI / Modern Dev tool

Render prompt templates with variable substitution. Part of the DevTools Surf developer suite. Browse more tools in the AI / Modern Dev collection.

Use Cases

Build reusable prompt libraries for team workflows
Test prompt variations with different variable inputs
Prepare parameterized prompts for API automation
Document prompt templates for non-technical teammates

Tips

Define variables with {{name}} syntax for substitution
Test edge cases by swapping variable values quickly
Preview the final rendered prompt before sending to an API

Fun Facts

Prompt engineering became a recognized job title in 2023, with salaries reaching $300,000 at major AI companies.
The Mustache template syntax ({{ }}) was created by Chris Wanstrath of GitHub in 2009 and inspired countless template engines.
Research from Microsoft in 2023 showed that structured prompt templates can improve LLM accuracy by up to 30% on reasoning tasks.

FAQ

What's template syntax?: Mustache-style `{{variable}}` substitution. Plus `{{#list}}...{{/list}}` for list iteration. Simple, widely understood, no escaping required.
Can I include conditionals?: Basic ones: `{{#if variable}}...{{/if}}`. For complex logic, process the data in code before templating rather than building logic into the template.
Does it validate variable coverage?: Yes — warns if the template has variables your data doesn't provide. Prevents 'Hello {{name}}!' sending literally to users when `name` is missing.
Is this Jinja2 or Handlebars?: Mustache-compatible subset. Works across Python (chevron, pystache), JS (Mustache.js), and most other languages. Portable templates.

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