Eta review
An open-source JavaScript engine for layouts, partials, and async rendering across runtimes.
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
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.
Eta pros and cons
- 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
Eta fact sheet, pricing and score →
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