Handlebars

Handlebars is a minimal templating engine for JavaScript that builds semantic templates effectively with no frustration, widely used across the JavaScript ecosystem for server-side rendering, email generation, static site generation, and configuration file templating. Created by Yehuda Katz in 2011, the library is largely compatible with Mustache templates, meaning that in most cases existing Mustache templates can be used directly by swapping the underlying engine without modification. The syntax uses double curly braces for expressions and supports features beyond the basic Mustache specification including block helpers with hash arguments, path expressions for traversing nested object properties, subexpressions for chaining helper invocations within a single expression, and triple curly braces for unescaped HTML output. The helper system is extensible through both built-in helpers like each, if, unless, with, and lookup, and custom helpers registered via the registerHelper API for domain-specific logic. Partial templates enable component reuse through the partial registration system and inline partial definitions, supporting layout inheritance patterns. Templates are compiled into optimized JavaScript functions at build time or runtime, making template execution faster than most other template engines by avoiding repeated parsing overhead. The precompiler produces smaller runtime bundles by eliminating the compiler dependency in production. The decorator system allows meta-programming of template execution, and strict mode enforces data access policies. Handlebars is used as the template engine for Ember.js, Ghost, Discourse, and thousands of Node.js applications. MIT licensed. Copyright 2011-2026 Yehuda Katz.