Why I think Web Containers are such a big deal, and how they’re changing the AI coding landscape

Back in 2021 a startup in San Francisco called Stackblitz introduced Web Containers, a way to run Node.js directly in the browser. While it was revolutionary at the time, the real power of Web Containers wasn’t fully unleashed until the company launched Bolt.new, an AI coding platform that is enabling an entirely new ecosystem of builders.

I like to think of Bolt.new, like Squarespace or Wix except rather than being limited just to websites (which you can build with Bolt), it extends to full stack applications.

While there’s a lot of magic that allows Bolt to do what it does, Web Containers are a key innovation and I felt like it was time to do a little history lesson into how this foundational technology got to where it is today.

So let’s jump in our time machine and go back to May of 2021 and this blog post from Eric.

A few years ago we realized that the web was heading towards a key inflection point. The advent of WebAssembly and new capabilities APIs made it seem possible to write a WebAssembly-based operating system powerful enough to run Node.js, entirely inside your browser. We envisioned a superior development environment that was faster, more secure and consistent than local environments, to enable seamless code collaboration without ever having to set up a local environment.

This sounded far-fetched. But if the web now runs full environments for graphic designers, video editors, and rich document editing, we wondered: is it finally possible for developers to use the web to build the web?

We decided to give it a shot. We hoped for the best, and expected the worst. Two years later (time flies 😅), the result has shaped up to be unexpectedly phenomenal. (Source — Stackblitz Blog)

The first use-case for Web Containers was Stackblitz’s core product, an instant full-stack IDE. The concept was simple but powerful — “Now you can use the web to build the web.”

Web Containers changed the game in many ways that most people might not have even noticed, they powered experiences we all got used to and likely didn’t even realize were there. Think of coding tutorials — with WebContainers companies could now build fully-contained tutorials that allowed people to learn concepts and test them directly in the browser without requiring them to get everything running on their local machine.

A great example of Web Containers in action in this context is learn.svelte.dev

If you think about it, this created a paradaigm shift that in many ways enabled a new way of learning how to code. Prior to Web Containers, learning how to code also meant learning how to setup a local environment, dealing with $PATH variable issues, version conflicts, etc.

Web Containers made it much easier for people to dive in and start learning core coding concepts without worrying about all the backend setup, and that’s kinda a big deal.

Okay so now let’s get to the good stuff — why would you want to run Node.js in the browser?

Here’s three pretty compelling reasons:

1. Faster than local — yes, running Node.js in the browser is actually faster for both builds and package installs. And I mean, a lot faster with package installs running 5x faster in the browser 🤯
2. Debug in-browser — since you’re running Node directly from the browser you don’t have to worry about adding any any extensions, and seamless integration with Chrome DevTools means you get native backend debugging 🐞
3. Super secure — this is one piece of the puzzle I think most people miss. Using Node.js in-browser is a lot more secure than running on your own machine because all code execution happens inside the browsers security sandbox 🔒

But for me the biggest win is not having to setup your local environment and then continue to manage and upgrade packages over time. Instead you get an environment that’s always up-to-date, is always secure, and just works.

Of course, not everyone loves Web Containers, and this post on Hacker News definitely got some attention 😳

What’s pretty neat is that Eric, the founder and CEO of Stackblitz actually jumped into the comments and gave a pretty awesome response.

Today, Web Containers are the magic behind Bolt.new one of the fastest growing AI coding tools on the planet. What’s neat about Bolt is you can build full-stack apps (with things like database integration w/Supabase) without knowing how to write a single line of code.

But…since Web Containers are rocking behind-the-scenes, if you do know how to code, you can dive into the code, make changes and then see your changes instantly in-browser.

And this week Bolt announced a partnership with Expo that now allows their platform to go a step further by allowing anyone to go right from prompt to app store, which is pretty wild if you take a second to think about that.

And yes, without Web Containers, none of this magic would be as magical. It’s an innovation that’s enabling an entirely new way to build software and it’s safe to say, there’s more to come — these are still the early days.

Okay, well we just got a huge snowstorm in Tahoe so it’s time for me to stop writing and start shoveling ⛏️ ❄️

(there’s no proper shovel emoji so a pick axe will have to do there!)