When comparing Handlebars.js vs Marko, the Slant community recommends Handlebars.js for most people. In the question“What are the best JavaScript templating engines?” Handlebars.js is ranked 2nd while Marko is ranked 10th. The most important reason people chose Handlebars.js is:
Handlebars is available as a JavaScript library, a [Django](https://github.com/yavorskiy/django-handlebars) module as well as [Java](https://github.com/jknack/handlebars.java), [Ruby](https://github.com/MSch/handlebars-ruby), [Scala](https://github.com/mwunsch/handlebars.scala), [.Net](https://github.com/rexm/Handlebars.Net) & [PHP](https://github.com/zordius/lightncandy) libraries, which means you can use it for frontend and backend templating in the language of your choice.
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Pros
Pro Clean syntax
Handlebars's syntax is very readable and easy to understand.

Pro Clear separation of logic and markup
If something is not within {{
and }}
, it's not Handlebars. As a result, Handlebars "weaves" through HTML, instead of trying to become an invalid extension of it.
Pro Copy/Paste code from the internet
Examples for Bootstrap or other CSS frameworks are always in HTML. With Handlebards you can just copy and paste the examples in your code. With something like Pug (Jade) you have to convert the HTML to Pug (Jade) first.
Pro Easy to use for templating things other than HTML
The syntax allows the output to be any text and does not contrain the user to HTML output only. There are examples of handlebars being used to produce SQL, javascript and other programming language code.
Pro Easy to use any template also as partials
Templates may be nested and reusable parts can be factored out.
Pro Compiled rather than interpreted templates
Handlebars.js allows you to pre-compile your templates so that the loading time at the client end could be reduced when your templated page is loaded.
Pro Mustache compatible
You can import Mustache templates and add extra functionality, that's provided by Handlebars, on top of them.
Pro Good global helpers support
Pro Logic-less
By design, logic-less templates force you to separate concerns thus helping you avoid future problems with refactoring. It also allow templates to be used with multiple programming languages without changes.
Pro Good paths support
With Handlebars.js you can create bindings with variables inside any path in your application.
Pro Easy to define extensions
With a few lines of code, a new extension (control or templating function) can be implemented. It will be called by the compiled templates.
Pro Extremely fast
Marko consistently outperforms other alternatives in code benchmarks, both on rendering speed and compilation time.
Pro Custom tags
Custom tags provide a simple mechanism for embedding more complex components into a template by extending the HTML grammar with support for new tags. For example:
<div>
<say-hello name="World"/>
</div>
Custom tags are easy to create since they just map to a JavaScript "renderer" function as shown below:
module.exports = function sayHelloRenderer(input, out) {
out.write('Hello ' + input.name + '!');
}
Custom tags support nested content:
<fancy-overlay title="My Title">
This will be the body content of the overlay
</fancy-overlay>
Custom tags can also have parent/child relationships to support more complex use cases such a "tabs" component with nested "tab" components:
<fancy-tabs>
<fancy-tabs:tab label="Home">
Content for Home
</fancy-tabs:tab>
<fancy-tabs:tab label="Profile">
Content for Profile
</fancy-tabs:tab>
<fancy-tabs:tab label="Messages">
Content for Messages
</fancy-tabs:tab>
</fancy-tabs>
Pro Streaming
Streaming allows progressive HTML rendering and reduces time to first byte.
Pro Server-side rendering
Marko supports both server-side and client-side rendering.
Pro Marko Widgets
Marko Widgets allows UI components (rendering + behavior) to be built using Marko.
Pro Compiled templates are readable CommonJS modules
Avoids ugly globals and "named" templates.
var template = require('./template.marko');
var html = template.renderSync({name: 'Frank'});
Pro Asynchronous rendering
Marko makes additional asynchronous calls after the view rendering has begun.
Pro Lightweight runtime (~4 KB gzip)
Pro Easy to integrate with express.js
Easy Integration with Express and Node
Pro Documentation is well maintained and helpful
The documentation is extensive and very helpful. It also contains several sample applications which are very useful.
Pro Allows JavaScript expressions
JavaScript expressions can be executed inside the templates.
Pro Simple and readable syntax
Marko has a HTML-like syntax which should be easy to read and understand for everyone who has even minimal experience in web development.
Pro Short learning curve
It is easy to get up to speed and understand what is going on in a very short period of time.
Pro Small compiled templates
Marko's compiled templates are usually very small, as proven by benchmarks.
Pro Lots of tests
To prevent regressions, Marko includes a full suite of tests. The testing harness renders a collection of templates and does an exact string comparison to make sure that the tests rendered exactly as expected. There are also API tests, and negative tests to make sure that errors are reported in a friendly way.
To run tests:
git clone https://github.com/marko-js/marko
cd marko
npm install
npm test
Pro Friendly compile-time error messages
Error messages come in an easy to read and friendly format, with valid stack traces and file formats of the file(s) which brought the error(s).

Pro Concise and Mixed syntax
The Concise syntax type lets you write Marko with a Jade-like indentation based syntax, and the Mixed mode lets you combine in regular HTML-style syntax.
Pro Server and client logic can easily be expressed within the same template
Pro Has a very active and interactive community
Marko's development community is rather small compared to other frameworks but community is well mannered and active. You can chat with the core development team using gitter.im
Cons
Con Hard to use documentation
Although the documentation exists and is fairly comprehensive, it's not always clearly written, and there is no search capacity.
Con Handlebars are still an HTML code
Handlebars use the standard HTML syntax with its own {{tags}} for templating. This doesn't add much to readability or design speed.
Con Using partials is cumbersome
"In order to use a partial, it must be registered" using some JavaScript method attached to some global variable.
Con Not much editor support
Handlebars.js doesn't seem to have many text editors that support things like auto-complete, syntax highlighting or error checking for it.
Con Does not play well with Angular.js
.. or any framework where you wish to compile handlebars.js template to the template understanable by the framework.
Con If you want to get the full experience you have to use NodeJS
To use markojs's most popular feature: SSR although you can use any language based server as a backend. It is rather complicated.
Con Very opinionated and not customizable enough
Some custom use cases are not possible. For example, trying to build an AMP page using Marko can be very challenging (special style tag requirements are hard to work with, also, Marko by default inserts a script tag into the rendered output html which is invalid in AMP and needs to be manually removed, etc..)
