#ui #dom #app #reactive #frontend


The minimal, obvious, graphical, web application interface

18 releases

new 0.3.4 Nov 20, 2020
0.2.3 Jun 5, 2020
0.2.1 Mar 27, 2020
0.1.3 Dec 28, 2019
0.0.1 Nov 28, 2019

#25 in GUI

Download history 3/week @ 2020-08-04 48/week @ 2020-08-11 15/week @ 2020-08-18 15/week @ 2020-08-25 19/week @ 2020-09-01 27/week @ 2020-09-08 1/week @ 2020-09-15 1/week @ 2020-09-22 20/week @ 2020-09-29 6/week @ 2020-10-06 3/week @ 2020-10-13 20/week @ 2020-10-20 8/week @ 2020-10-27 68/week @ 2020-11-03 54/week @ 2020-11-10 26/week @ 2020-11-17

84 downloads per month
Used in mogwai-hydrator

MIT license

2.5K SLoC


minimalist, obvious, graphical web application interface

release: Crates.io cicd

master: cicd

mogwai is a frontend DOM library for creating web applications. It is written in Rust and runs in your browser and has enough functionality server-side to do rendering. It is an alternative to React, Backbone, Ember, Elm, Purescript, etc.



  • provide a declarative approach to creating and managing DOM nodes
  • encapsulate component state and compose components easily
  • explicate DOM updates
  • be small and fast (snappy af)

If mogwai achieves these goals, which I think it does, then maintaining application state, composing widgets and reasoning about your program will be easy. Furthermore, your users will be happy because their UI is snappy!


The main concepts behind mogwai are

  • channels instead of callbacks - view events like clicks, blurs, etc are transmitted into a channel instead of invoking a callback. Receiving ends of channels can be branched and may have their output messages be mapped, filtered and folded. mogwai's channels are many-producer, many-consumer and are immediate - they do not perform buffering and do not require polling.

  • views are dumb - a View is just a bit of DOM that receives and transmits messages. When a View goes out of scope and is dropped in Rust, it is also dropped from the DOM. Views may be constructed and nested using plain Rust functions or an RSX macro.

  • widgets are folds over input messages - the user interface widget in mogwai is a Gizmo. The Gizmo type holds an internally mutable state and can communicate messages to its View, which may live out in the DOM. Its View can send messages back to the Gizmo, which triggers the Gizmo's update function. The Gizmo's update function can mutate the state variable and send output messages to the View, which in turn updates the DOM.

  • communication is easy - just gizmo.send(&my_message) to send a message into a gizmo and the gizmo will run its update logic and patch the view accordingly.


Here is an example of a button that counts the number of times it has been clicked:

use mogwai::prelude::*;

pub struct Button {
    pub clicks: i32

pub enum ButtonIn {

pub enum ButtonOut {

impl Component for Button {
    type ModelMsg = ButtonIn;
    type ViewMsg = ButtonOut;
    type DomNode = HtmlElement;

    fn update(
        &mut self,
        msg: &ButtonIn,
        tx_view: &Transmitter<ButtonOut>,
        _subscriber: &Subscriber<ButtonIn>
    ) {
        match msg {
            ButtonIn::Click => {
                self.clicks += 1;
                let text = if self.clicks == 1 {
                    "Clicked 1 time".to_string()
                } else {
                    format!("Clicked {} times", self.clicks)

    // Notice that the `Component::view` function returns a `ViewBuilder<T>` and not
    // a `View<T>`.
    fn view(
        tx: &Transmitter<ButtonIn>,
        rx: &Receiver<ButtonOut>
    ) -> ViewBuilder<HtmlElement> {
        let tx_event = tx.contra_map(|_:&Event| ButtonIn::Click);
        let rx_text = rx.branch_map(|ButtonOut::Clicks(text)| text.clone());

            // Create a button that transmits a message into tx_event on click.
            <button on:click=tx_event>
                // Using braces we can embed rust values in our DOM.
                // Here we're creating a text node that starts with the
                // string "Clicked 0 times" and then updates every time a
                // message is received on rx_text.
                {("Clicked 0 times", rx_text)}
// To create a new gizmo/widget/component we simply convert a value of the Button type
// into a Gizmo...
let gizmo = Gizmo::from(Button{ clicks: 0 });
// ...and create a View from that gizmo's builder.
let view = View::from(gizmo.view_builder());
// Queue some messages for the component, as if the button had been clicked:

assert_eq!(&view.html_string(), "<button>Clicked 2 times</button>");

if cfg!(target_arch = "wasm32") {
    // running a view adds its DOM to the document.body and ownership is passed to the window,
    // so this only works in the browser

// After handing off the view the gizmo itself may fall out of scope and be dropped. The
// view is all that is needed for your app to run.


If you're interested in learning more - please read the introduction and documentation.


Rust is beginning to have a good number of frontend libraries. Many encorporate a virtual DOM with a magical update phase. Even in a language that has performance to spare this step can cause unwanted slowness and can be hard to reason about what is updating, exactly.

In mogwai, channel-like primitives and a declarative view builder are used to define components and then wire them together. Once the interface is defined and built, the channels are effectively erased and it's functions all the way down. There's no performance overhead from vdom, shadow dom, polling or patching. So if you prefer a functional style of programming with lots of maps and folds - or if you're looking to go vroom! then maybe mogwai is right for you :)

Please do keep in mind that mogwai is still in alpha and the API is actively changing - PRs, issues and questions are welcomed.

made for rustaceans, by a rustacean

mogwai is a Rust first library. There is no requirement that you have npm or node. Getting your project up and running without writing any javascript is easy enough.


mogwai is snappy! Here is some very handwavey and sketchy todomvc benchmarketing:

mogwai performance benchmarking

ok - where do i start?

First you'll need new(ish) version of the rust toolchain. For that you can visit https://rustup.rs/ and follow the installation instructions.

Then you'll need wasm-pack.

For starting a new mogwai project we'll use the wonderful cargo-generate, which can be installed using cargo install cargo-generate.

Then run

cargo generate --git https://github.com/schell/mogwai-template.git

and give the command line a project name. Then cd into your sparkling new project and

wasm-pack build --target web

Then, if you don't already have it, cargo install basic-http-server or use your favorite alternative to serve your app:

basic-http-server -a

Happy hacking! ☕ ☕ ☕

more examples please

For more examples, check out

the sandbox

the todomvc app

the benchmark suite

To build the examples use:

cd examples/whatever && wasm-pack build --target web

external examples

mogwai-realworld A "real world" app implementation (WIP)


📗 Cooking with Mogwai is a series of example solutions to various UI problems. It aims to be a good reference doc but not a step-by-step tutorial.

group channel ☎️

Hang out and talk about mogwai in the support channel:


Please consider sponsoring the development of this library!


~160K SLoC