Eta
Eta: An open-source JavaScript engine for layouts, partials, and async rendering across runtimes. Ranked #34 of 65 in Template Engine Software by our editors (6.1/10); pricing: Free plan; best for javaScript teams needing async layouts and partials.
At a glance
- Editor score6.1 / 10
- PricingFree plan
- Best forJavaScript teams needing async layouts and partials
- Free planYes
- Paid fromFree
- Rendering modeBoth
- Facts checked23 Oct 2026
Where it wins
- Renders in Node, Deno, and browsers, on server or client
- Supports partials, layouts, nested layouts, and custom delimiters
- Includes async rendering, caching, and default output escaping
Where it doesn't
- Templates execute as JavaScript and are not sandboxed
- It is a library, not a hosted template service
- Support is through community resources and documentation
Our verdict on Eta
Eta is an open-source template engine written in TypeScript for developers working in Node, Deno, or a browser. It compiles template syntax into functions and can render on the server or client, making it relevant to JavaScript teams that want layouts and partials across those environments. Its logic-based syntax supports JavaScript expressions, and configurable delimiters let teams adjust template syntax. Eta is a library rather than a hosted service, so it fits teams prepared to incorporate a rendering engine into their own applications.
The feature set covers more than basic interpolation: Eta supports partial templates, layouts and nested layouts, plugins, caching, and asynchronous rendering. It can be integrated with Express.js, Fastify, and Deno. Automatic escaping is enabled by default for interpolated output, which is useful for common rendering workflows. Templates themselves execute as JavaScript, however, and Eta does not sandbox that execution. That distinction matters for teams deciding what template authors or inputs they can trust; it should not be treated as an isolated environment for untrusted templates.
Eta is distributed as open-source software, with no paid tiers described here, and deployment can be cloud-based or self-hosted as part of an application. Documentation and community resources are its support channels. Its runtime range and inheritance features make it a fit for teams seeking a compact engine with async rendering, while organizations that require sandboxed template execution or a hosted service should look elsewhere. Teams comfortable owning integration and operational decisions can choose it for its cross-runtime support and template composition features.
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Eta pricing
Eta fact sheet
| Free plan | Yes |
|---|---|
| Paid from | Free |
| Rendering mode | Both |
| Syntax model | Logic-based |
| Template inheritance | Yes |
| Automatic escaping | Yes |
| Sandbox mode | No |
| Async rendering | Yes |
| License model | Open-source |
| Deployment | Cloud, Self-hosted |
| Platforms | Web |
| Support | Community, Docs |
| Built for | Solo, Small business, Mid-market, Enterprise (editorial estimate) |
| Integrations | 3 integrations: Express.js, Fastify, Deno See all → |
| Pricing | Free plan |
| Website | eta.js.org |
| Facts checked | 23 Oct 2026 |
Eta integrations
Eta lists 3 integrations on its own site.
- Express.js
- Fastify
- Deno
Alternatives to Eta
- JinjaJinja gives Python applications inheritance, configurable rendering, and compilation in an open-source engine.9.4
- TwigA free, open-source PHP engine for compiled templates, inheritance, escaping, and sandboxing.9.3
- Handlebars.jsA free, open-source template engine for JavaScript projects that need reusable HTML.9.2
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Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
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