The thing I most want to use this (or some other WASM Linux engine) for is running a coding agent against a virtual operating system directly in my browser.
Claude Code / Codex CLI / etc are all great because they know how to drive Bash and other Linux tools.
The browser is probably the best sandbox we have. Being able to run an agent loop against a WebAssembly Linux would be a very cool trick.
I had a play with v86 a few months ago but didn't quite get to the point where I hooked up the agent to it - here's my WIP: https://tools.simonwillison.net/v86 - it has a text input you can use to send commands to the Linux machine, which is pretty much what you'd need to wire in an agent too.
In that demo try running "cat test.lua" and then "lua test.lua".
> The thing I most want to use this (or some other WASM Linux engine) for is running a coding agent against a virtual operating system directly in my browser.
Apptron uses v86 because its fast. Would love it for somebody to add 64-bit support to v86. However, Apptron is not tied to v86. We could add Bochs like c2w or even JSLinux for 64-bit, I just don't think it will be fast enough to be useful for most.
Apptron is built on Wanix, which is sort of like a Plan9-inspired ... micro hypervisor? Looking forward to a future where it ties different environments/OS's together.
https://www.youtube.com/watch?v=kGBeT8lwbo0
tldr; devcontainers let you completely containerize your development environment. You can run them on Linux natively, or you can run them on rented computers (there are some providers, such as GitHub Codespaces) or you can also run them in a VM (which is what you will be stuck with on a Mac anyways - but reportedly performance is still great).
All CLI dev tools (including things like Neovim) work out of the box, but also many/most GUI IDEs support working with devcontainers (in this case, the GUI is usually not containerized, or at least does not live in the same container. Although on Linux you can do that also with Flatpak. And for instance GitHub Codespaces runs a VsCode fully in the browser for you which is another way to sandbox it on both ends).
This is interesting (and I've seen it mentioned in some editors), but how do I use it? It would be great if it had bubblewrap support, so I don't have to use Docker.
Do you know if there's a cli or something that would make this easier? The GitHub org seems to be more focused on the spec.
Sorry for the off-topic, but what a bliss to see Windows 2000 interface. And what an absolute abomination from hell pretty much all the modern UIs are.
It looks like container2wasm uses a forked version of Bochs to get the x86-64 kernel emulation to work. If one pulled that out separately and patched it a bit more to have the remaining feature support it'd probably be the closest overall. Of course one could say the same about patching anything with enough enthusiasm :).
> Access to Internet is possible inside the emulator. It uses the websocket VPN offered by Benjamin Burns (see his blog). The bandwidth is capped to 40 kB/s and at most two connections are allowed per public IP address. Please don't abuse the service.
We are a playful species. People enjoy play. If we didn't have to work for a living but still enjoyed food security that is all most of us would do. But we are also a very exploitative species, some more than others. Companies have made billions of dollars on top of Fabrice Bellard's works, qemu, ffmpeg etc.
These companies don't have any imagination. Their management has no vision. They could not create anything new and wonderful if they tried. People like Fabrice do and we are all richer for it. If your asking about the practical use you are likely in the exploitative mindset which is understandable on HN. The hacker/geek mindset enjoys this for what it is.
I use bellard.org/jslinux to test compilation of strange code sometimes[1], since it came with compilers that are different versions from what I have installed locally, and it's easier to open up a browser than starting a VM.
I use a similar emulator (v86) as a way to share my hobby OS. Approximately zero people, even my friends, are going to boot my hobby OS on real hardware; I did manage to convince some of them to run it in qemu, but it's difficult. A browser environment shows the thing quite well; and easy networking is cool too.
My hobby OS itself is not very useful, but it's fun if you're in the right mood.
Working with VMs always felt difficult because of this. So authoring was built-in to Docker. Now you can use Apptron to author and embed a Linux system on a web page. This aspect is usable, but it's only going to get better.
Most such emulators have Internet access on the IP level. Therefore, this is a very cheap way to test anything on the Internet.
apk add nmap
nmap your.domain.com
However, the speed is heavily throttled. You can even use ssh and login to your own server.
It can also be used as a very cheap way to provide a complete build environment on a single website, for example to teach C/C++. Or to learn the shell. You don't have to install anything.
Agentic workloads create and then run code. You don't want to just run that code in a "normal" environment like a container, or even a very well protected VM. There are other options, ofc - eg. gvisor, crossvm, firecracker, etc, but this one is uncommon enough to have a small number of attackers trying to hack it.
What's wrong with a well protected VM? Especially compared to something where the security selling point is "no one uses it" (according to your argument; I don't know how secure this actually is)
Yeah but GP was answering to a comment saying "you don't want to run code in a well protected VM". Which is of course complete non sense to say and GP was right to question it.
Maybe if you’ve got some ancient software that’s missing source code and only runs with X Y and Z conditions, you could continue to offer it on the web and build around it like that? Not sure if that would be practical at all, but could be interesting
The thing I most want to use this (or some other WASM Linux engine) for is running a coding agent against a virtual operating system directly in my browser.
Claude Code / Codex CLI / etc are all great because they know how to drive Bash and other Linux tools.
The browser is probably the best sandbox we have. Being able to run an agent loop against a WebAssembly Linux would be a very cool trick.
I had a play with v86 a few months ago but didn't quite get to the point where I hooked up the agent to it - here's my WIP: https://tools.simonwillison.net/v86 - it has a text input you can use to send commands to the Linux machine, which is pretty much what you'd need to wire in an agent too.
In that demo try running "cat test.lua" and then "lua test.lua".
> The thing I most want to use this (or some other WASM Linux engine) for is running a coding agent against a virtual operating system directly in my browser.
That exists: https://github.com/container2wasm/container2wasm
Unfortunately I found the performance to be enough of an issue that I did not look much further into it.
Simon, this HN post didn't need to be about Gen AI.
This thing is really inescapable those days.
Parallel thread: https://news.ycombinator.com/item?id=47311484#47312829 - "I've always been fascinated by this, but I have never known what it would be useful for."
I should have replied there instead, my mistake.
Check out Jeff Lindsay's Apptron (https://github.com/tractordev/apptron), comes very close to this, and is some great tech all on its own.
It's getting there. Among other things, it's probably the quickest way to author a Linux environment to embed on the web: https://www.youtube.com/watch?v=aGOHvWArOOE
Apptron uses v86 because its fast. Would love it for somebody to add 64-bit support to v86. However, Apptron is not tied to v86. We could add Bochs like c2w or even JSLinux for 64-bit, I just don't think it will be fast enough to be useful for most.
Apptron is built on Wanix, which is sort of like a Plan9-inspired ... micro hypervisor? Looking forward to a future where it ties different environments/OS's together. https://www.youtube.com/watch?v=kGBeT8lwbo0
This is not the technical solution you want, but I think it provides the result that you want: https://github.com/devcontainers
tldr; devcontainers let you completely containerize your development environment. You can run them on Linux natively, or you can run them on rented computers (there are some providers, such as GitHub Codespaces) or you can also run them in a VM (which is what you will be stuck with on a Mac anyways - but reportedly performance is still great).
All CLI dev tools (including things like Neovim) work out of the box, but also many/most GUI IDEs support working with devcontainers (in this case, the GUI is usually not containerized, or at least does not live in the same container. Although on Linux you can do that also with Flatpak. And for instance GitHub Codespaces runs a VsCode fully in the browser for you which is another way to sandbox it on both ends).
This is interesting (and I've seen it mentioned in some editors), but how do I use it? It would be great if it had bubblewrap support, so I don't have to use Docker.
Do you know if there's a cli or something that would make this easier? The GitHub org seems to be more focused on the spec.
Can I PLEASE click on ONE post on the front page of HN without immediately being met by some grifter trying to derail it to promote their AI product?
Please? I'm begging here.
We are working on exactly this: https://browserpod.io
For a full-stack demo see: https://vitedemo.browserpod.io/
To get an idea of our previous work: https://webvm.io
Sorry for the off-topic, but what a bliss to see Windows 2000 interface. And what an absolute abomination from hell pretty much all the modern UIs are.
win2000 brings back so many good memories.
Yeah. Microsoft really went downhill UI-wise.
Is that even remotely relevant to JSLinux?
Yes, it's one of the available emulated systems on JSLinux.
If you'd clicked the link, instead of just reading the title, you'd have known it was.
Unfortunately, he didn't attach the source code for the 64-bit x86 emulation layer, or the config used to compile the hosted image.
For a more open-source version, check out container2wasm (which supports x86_64, riscv64, and AArch64 architectures): https://github.com/container2wasm/container2wasm
https://github.com/copy/v86 might be a more 1:1 fully open sourced alternative.
Not really. x86_64 is not supported yet: https://github.com/copy/v86/issues/133
Sure, and there are probably some other things lacking, but JSLinux supports a lot more than CLI Linux userspace on x86-64 too. E.g. compare to lack of graphical interface https://github.com/container2wasm/container2wasm/issues/196
It looks like container2wasm uses a forked version of Bochs to get the x86-64 kernel emulation to work. If one pulled that out separately and patched it a bit more to have the remaining feature support it'd probably be the closest overall. Of course one could say the same about patching anything with enough enthusiasm :).
I love how nonchalantly demonstrates his custom terminal emulator and javascript engine.
Incredible guy!
I can launch this thing and start making arbitrary connections out to port 25 on the internet from some random IP? Hmm.
From the "Technical notes" page:
> Access to Internet is possible inside the emulator. It uses the websocket VPN offered by Benjamin Burns (see his blog). The bandwidth is capped to 40 kB/s and at most two connections are allowed per public IP address. Please don't abuse the service.
https://bellard.org/jslinux/tech.html
If anyone is interested, I made some modifications last month to get TempleOS running on the x86_64 JSLinux: https://ring0.holyc.xyz/
Wow, thanks for this, this is exactly what v86 was missing! Runs faster than my demo: https://zb3.me/qemu-wasm-test/jspi-noffi/
Even though it has no JIT. Truly magic :)
I've always been fascinated by this, but I have never known what it would be useful for. Does anyone know of any practical use cases?
We are a playful species. People enjoy play. If we didn't have to work for a living but still enjoyed food security that is all most of us would do. But we are also a very exploitative species, some more than others. Companies have made billions of dollars on top of Fabrice Bellard's works, qemu, ffmpeg etc.
These companies don't have any imagination. Their management has no vision. They could not create anything new and wonderful if they tried. People like Fabrice do and we are all richer for it. If your asking about the practical use you are likely in the exploitative mindset which is understandable on HN. The hacker/geek mindset enjoys this for what it is.
I use bellard.org/jslinux to test compilation of strange code sometimes[1], since it came with compilers that are different versions from what I have installed locally, and it's easier to open up a browser than starting a VM.
[1] For example:
https://www.ioccc.org/2020/yang/index.html#:~:text=tcc%200.9...
https://www.ioccc.org/2018/yang/index.html#:~:text=tcc%200.9...
I use a similar emulator (v86) as a way to share my hobby OS. Approximately zero people, even my friends, are going to boot my hobby OS on real hardware; I did manage to convince some of them to run it in qemu, but it's difficult. A browser environment shows the thing quite well; and easy networking is cool too.
My hobby OS itself is not very useful, but it's fun if you're in the right mood.
Some sort of web based archive of applications/etc where you can boot them up in your browser.
That’s what I’d like to use it for as well, but it’s difficult to do so because there’s no way to edit the disk image.
Any advice on how to create a JSLinux clone with a specific file pre-installed and auto-launching would be much appreciated!
Working with VMs always felt difficult because of this. So authoring was built-in to Docker. Now you can use Apptron to author and embed a Linux system on a web page. This aspect is usable, but it's only going to get better.
Most such emulators have Internet access on the IP level. Therefore, this is a very cheap way to test anything on the Internet.
However, the speed is heavily throttled. You can even use ssh and login to your own server.It can also be used as a very cheap way to provide a complete build environment on a single website, for example to teach C/C++. Or to learn the shell. You don't have to install anything.
You need backend proxies, the browser doesn't allow ignoring CORS by default.
Agentic workloads create and then run code. You don't want to just run that code in a "normal" environment like a container, or even a very well protected VM. There are other options, ofc - eg. gvisor, crossvm, firecracker, etc, but this one is uncommon enough to have a small number of attackers trying to hack it.
What's wrong with a well protected VM? Especially compared to something where the security selling point is "no one uses it" (according to your argument; I don't know how secure this actually is)
Nothing, but "there are already working options" does not necessarily mean we shouldn't try new (and sometimes weird) things
GP says "You don't want to just run that code in ... even a very well protected VM." Why?
Yeah but GP was answering to a comment saying "you don't want to run code in a well protected VM". Which is of course complete non sense to say and GP was right to question it.
Maybe if you’ve got some ancient software that’s missing source code and only runs with X Y and Z conditions, you could continue to offer it on the web and build around it like that? Not sure if that would be practical at all, but could be interesting
My college professor used it to teach us the Linux command line
We have Windows PCs in the classroom.
Similarly I've used it for technical interviews.
How do TinyEmu and JSLinux compare to linux-wasm?
From "Show HN: Amla Sandbox – WASM bash shell sandbox for AI agents" (2026) https://news.ycombinator.com/item?id=46825119 :
>>> How to run vscode-container-wasm-gcc-example with c2w, with joelseverin/linux-wasm?
>> linux-wasm is apparently faster than c2w
From "Ghostty compiled to WASM with xterm.js API compatibility" https://news.ycombinator.com/item?id=46118267 :
> From joelseverin/linux-wasm: https://github.com/joelseverin/linux-wasm :
>> Hint: Wasm lacks an MMU, meaning that Linux needs to be built in a NOMMU configuration
From https://news.ycombinator.com/item?id=46229385 :
>> There's a pypi:SystemdUnitParser.
He builds epicness.
UBY: touchscreen: How to scroll the scrollback