Nunjucks
Jinja2-inspired templating engine for JavaScript from Mozilla. Nunjucks supports template inheritance (extends/block), macros, custom filters, async rendering, and has a richer feature set than Handlebars while remaining logic-friendly. Used for server-side HTML rendering, static site generation, and complex document generation where Handlebars' minimal logic is too restrictive.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
XSS risk if autoescape not enabled. Sandbox mode is incomplete — do not execute untrusted Nunjucks templates. Template data should not include sensitive values in output context.
⚡ Reliability
Best When
You need a feature-rich server-side templating engine in Node.js with template inheritance, macros, and custom filters — especially if your team knows Jinja2.
Avoid When
You need React-style component composition for interactive UIs or minimal templating without the Jinja2 feature set.
Use Cases
- • Render complex HTML pages in agent web applications using Nunjucks template inheritance for shared layouts with per-page content blocks
- • Generate configuration files and documents with Nunjucks macros for reusable template components across agent output pipelines
- • Build static site generators using Nunjucks' file-based template system with async data loading and custom filters
- • Create Jinja2-compatible templates for teams with Python background — Nunjucks syntax is intentionally close to Jinja2
- • Generate structured agent reports and exports with Nunjucks filters for date formatting, number rounding, and string transformation
Not For
- • Security-critical untrusted template rendering — Nunjucks templates can execute filters and macros; sandbox mode exists but has limitations
- • React/Vue component UIs — server-side templating is for document generation, not interactive client-side UIs
- • High-performance streaming rendering — Nunjucks rendering is synchronous by default; async mode requires callbacks, not Promises
Interface
Authentication
No authentication — local templating library.
Pricing
Nunjucks is open source, free, and maintained by Mozilla.
Agent Metadata
Known Gotchas
- ⚠ Nunjucks renders undefined variables as empty string by default — enable throwOnUndefined: true for strict mode to catch missing data instead of silently producing empty content
- ⚠ Async filters require the callback pattern in Nunjucks async mode — Promises aren't natively supported in filter definitions; wrap async operations in addFilter with done callback
- ⚠ Template caching is enabled by default in production — file changes require process restart; set noCache: true in development or reload FileSystemLoader
- ⚠ Nunjucks has no automatic XSS escaping like Handlebars — call nunjucks.configure(templates, {autoescape: true}) explicitly; raw HTML in variables otherwise renders unescaped
- ⚠ Template inheritance (extends) requires the parent template to define blocks — a base template without block definitions can't be overridden by child templates
- ⚠ Nunjucks sandbox mode exists but is not comprehensive — untrusted user templates still have access to global objects; do not run user-supplied templates in production without sandboxing review
Alternatives
Full Evaluation Report
Detailed scoring breakdown, competitive positioning, security analysis, and improvement recommendations for Nunjucks.
Scores are editorial opinions as of 2026-03-06.