Liquid
Templating language created by Shopify in 2006. Safe (sandboxed) — lets customers write templates without executing arbitrary code. Tobi Lütke (Shopify CEO) wrote the original.
Usage: Shopify theme system, Jekyll static site generator, GitHub Pages, Salesforce Marketing Cloud. Three constructs: {{ output }}, {% logic %}, {# comment #}. Distinct from Jinja2/Handlebars: more restrictive, more secure. Liquid Drops are Ruby objects exposed to templating. Useful pattern for let-users-write-templates-without-RCE-risk.