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Feb 7, 2018

Announcing CodeSandbox 2.5

Announcing: Angular Support, Jest Integration, New Streamlined Editor, State Management Rewrite, Babel Plugin Support and much more!

Ives van Hoorne
Ives van Hoorne
Announcing CodeSandbox 2.5

It's February and high time for a new big update for CodeSandbox! We've been very quiet the past month, but we were not sitting still. This update is packed with new features, I believe this is the biggest update to date, by far. And the best part is that many contributors helped with this update!

We have more than 20 new features, a redesign and a rewrite to show, so we better get started!

New Editor Design

As time passed by our UI became more and more cluttered. We lost simplicity for feature abundance and oftentimes it was hard to navigate and find the right button. We absolutely don't want this and used this as an excuse to go on a spiritual trip and redesign the editor 👨‍🎨. Again, like the homepage, we received a lot of help from Danny Ruchtie, props to him!

The new editor, in its full glory


A big improvement against the clutter is our new sidebar, inspired by Visual Studio Code. We now categorize all functionality under their function: 'Project Info', 'File Explorer', 'Deployment', 'GitHub' and 'Configuration Files'. The sidebar is only enabled when you're looking at your own sandbox.

The relevant items are behind the corresponding navigation

Edit/View Mode

We noticed that a lot of functionality was only really useful when you were editing your own sandbox. That's why we decided to have a separate 'View Mode'. This mode only shows the sandbox info, the files and the dependencies.

View mode highlights the information that's useful for viewers

Floating Preview

We've upgraded the preview by making it float! You can use the preview now as a window: you can resize and drag it anywhere. This makes it easier to do mobile development: you can resize the preview window to a phone size. This also allows for vertical split between code and preview.

You can put the preview wherever you want, you also see the size of the preview while you resize

Console Upgrades

Our console input received a big upgrade thanks to the work of Xiaoyi Chen (also the author of react-inspector). You can write multiline commands and now we also syntax highlight and autocomplete your inputs!

Syntax highlighting, checking and multiline commands

Rewrite to Cerebral

When we released CodeSandbox I got in touch with Christian Alfoni, the author of Cerebral and WebpackBin. We started working together on many different projects, and eventually started toying with the idea of converting CodeSandbox from Redux to Cerebral. Christian started working on this about three months ago, and it's finished now!

The start of the rewrite in October!

We now use Cerebral for state management, backed by mobx-state-tree. This gives us the declarative functional composition of the CodeSandbox application logic and typed observable state values for optimal rendering out of the box. It has resulted in more performance and a reaaaally nice debug view!

The debug view looks reaaaally nice

During the rewrite we also took the opportunity to implement several new optimistic updates for a smoother user experience.

You can read more about the complete rewrite here.

Configuration Support

Our stance on configuration is quite simple; configuration means that the program is too stupid to determine what the user wants. Oftentimes you can satisfy 90% of the user preferences without configuration.

However, there is still the other 10%, CodeSandbox as an application is a good example of this. That's why we are introducing official support for configuration files. Depending on the template, you can configure several aspects of your sandbox. The configurations we currently support are: package.json, .prettierrc, .babelrc, sandbox.config.json and .angular-cli.json.

Single Source of Truth

We previously saved dependencies, titles, etc. separately in our database. When you'd import a sandbox from GitHub we would get every relevant field from the files and save them manually in our database. This creates friction: when you add a dependency we need to manually update the database and update package.json.

From this update on we make the files our source of truth for almost all data, this means that sandbox data is parsed from package.json and other relevant configuration files live in the editor. We add this retroactively; when you open a sandbox we automatically generate a package.json if it doesn't exist.

The dependencies update live as you update package.json

Configuration UI

We are of the opinion that UI can be far more intuitive than code. That's why we aim to interfacivize (if that would be a word) all configuration files. We show a UI which you can use to generate code for the configuration files. We still allow you to switch to the code, if you want more control 😉. We don't have a UI for all configurations yet, but we show custom autocompletions for those configurations.

Use a UI to configure your files

Babel Plugin Support

A much requested feature was custom Babel plugins support, not only the official ones, but also community plugins. We now allow the configuration of .babelrc in the Preact template and will soon enable this in Vue and our upcoming 'Custom' sandbox. A cool addition to this is that we support the fs interface. This is especially useful for Babel plugins like babel-plugin-preval. Go ahead and try it!

Advanced Babel plugins like babel-plugin-macros that use fs are currently in beta. We will streamline Babel plugin support over the coming weeks, with a custom UI to search for plugins and the ability to create and select presets.

Sandbox Configuration

You can now configure your sandbox using sandbox.config.json. You can find more documentation about sandbox.config.json here.

Configuration options

Angular Template

Official Angular support was an often requested feature from day one. We now officially support Angular templates, including the corresponding angular-cli.json file that comes with it!

Give it a try here:

Or open it in the new editor!

Native Jest Support

We now have Jest support, mainly thanks to Gautam Arora! Gautam opened an issue for Jest integration about 2 months ago, and about a month later he opened a PR with a version that already could run all tests of the Redux examples.

The past week I've been working a native UI for Jest that fits with our redesign, and I'm really proud of how it turned out. I took inspiration from Majestic and Storybook. Let's see what it looks like.

You can find tests next to the console, this is a view with some errors

As you can see the files with tests are in the left navigator. When you select a test file you get the details of that file, including statuses and eventual errors.

This is how you can interact with the tests

We automatically watch all test files. If you change a file we will only rerun the tests that require this file, either directly or indirectly. We also support snapshot testing, though we're still working on the possibility to save new snapshots.

Snapshot reading working!

I'm really proud of the integration with Jest, and it was only possible because the Jest team did an incredible job by publishing all their functionality in separate packages. We just cherry picked the packages that we needed to make Jest work in the CodeSandbox! The Redux TodoMVC example is a good sandbox to play with Jest support.

Note that this is not fully native Jest, we don't support writing snapshots, manual mocks using the __mocks__ directory and Jest configuration yet. We will add this soon though.

CodeSandbox Bundler Upgrade

I did some upgrades to the bundler of CodeSandbox, the most notable improvements are caching and an official HMR API.

Compiler Cache

After every successful bundle we cache all relevant transpilation and files in IndexedDB. When you refresh the sandbox you only need to actually evaluate all the files instead of doing transpilation etc. This results in very fast initial load times, as you can see in this GIF.

Near instant reloading!

Hot Module Reloading API

We also now have official HMR support (finally!). You can use the API like in webpack, this is useful for when you want to preserve state between runs for example. We also added official support for the HMR API in our Vue loader, this means that Vue gets proper HMR out of the box!

Using HMR together with Redux to hot reload its state

Updates You Might Have Missed

We've had many updates recently. Here's a quick recap of some changes that happened in December:

Zen Mode

Zen mode hides all distracting elements, therefore it's perfect for presentations and course videos. You can enable it in preferences or by the keybinding.

Zen Mode enabled

Keybinding Support

You can now set up custom key bindings for actions in CodeSandbox!

Quick Actions

Quick Actions can be activated with (CMD/CTRL)-Shift-P and will show this as popup.

Just type and select!

It allows you to quickly active actions without touching your mouse or remembering a key binding.

CodeSandbox Documentation

To answer questions or explain CodeSandbox concepts we now have an official documentation.

You can follow either CodeSandbox or me on Twitter to keep up to date with any changes. We also keep a changelog here.

What's Next

Oh well, that was a big list of changes... The coming week I will concentrate mostly on my talk at Vue Amsterdam and fixing any bug that may pop up. However, we do have some exciting plans for the coming time!

Custom Template

We have support for many transpilers right now, but there is no template that supports all of them. We've seen that users want to experiment with different things like Babel plugins, but don't want to tie their sandbox to a template that's not related to their project. That's why we'll implement something called a Custom template in the near future. I've already done some work on this feature and wanted to release it with 2.5, but ran out of time. Bottom line is, it should be done soon 😃.

Hosting Migrations

We have grown a lot since we started. We want to have more scalability, so we will move our hosting over to Kubernetes.

We are also starting a big project that will start this February and will continue for the coming 3 months. I can't give any details on that project yet except for saying that it's an exciting change.


This update received a lot of support from contributors of CodeSandbox. I'm really thankful for all the work from others, and I'd like to especially thank Bogdan, Christian, Danny and Gautam for their work and support on this update.

Thanks to this list of contributors!

Want to get involved?

We're 90% (soon 100%) open source! We welcome any help with open arms. If you're interested in helping out, I recommend you to check out our client repo.

If you want to chat, we have an active Spectrum community.

Also, if you would like to support CodeSandbox financially, you can become a CodeSandbox Patron!

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