Liquid
Liquid is an open-source template engine created by Shopify, written in Ruby, that allows developers to embed dynamic content into static files like HTML, XML, or JSON. It uses a simple, readable syntax with tags, objects, and filters to separate logic from presentation, making it ideal for themes, emails, and configuration files. Liquid is safe for untrusted user input as it restricts direct code execution, preventing security vulnerabilities like code injection.
Developers should learn Liquid when building themes for e-commerce platforms like Shopify or Jekyll-based static websites, as it's the default templating language in these ecosystems. It's also useful for generating dynamic content in emails, invoices, or reports where security and simplicity are priorities, as its sandboxed environment minimizes risks from user-generated templates. In scenarios requiring non-technical users to edit templates, Liquid's intuitive syntax reduces errors compared to more complex engines.