X86-64 Playground – an Online Assembly Editor and Gdb-Like Debugger

Posted2 months agoActive2 months ago

modinfo

180 points

24 comments

x64.halb.itTechstory

supportivepositive

Debate

20/100

Assembly LanguageEmulationDebugging Tools

Key topics

Assembly Language

Emulation

Debugging Tools

The x86-64 Playground is an online assembly editor and debugger that has garnered positive attention from the HN community, with users praising its usefulness and discussing its technical aspects.

Snapshot generated from the HN discussion

Discussion Activity

Light discussion

First comment

Peak period

2-4h

Avg / period

2.4

Comment distribution24 data points

Loading chart...

Based on 24 loaded comments

Key moments

01Story posted
Oct 20, 2025 at 1:55 PM EDT
2 months ago
Step 01
02First comment
Oct 20, 2025 at 3:12 PM EDT
1h after posting
Step 02
03Peak activity
4 comments in 2-4h
Hottest window of the conversation
Step 03
04Latest activity
Oct 21, 2025 at 11:39 AM EDT
2 months ago
Step 04

Generating AI Summary...

Analyzing up to 500 comments to identify key contributors and discussion patterns

Discussion (24 comments)

Showing 24 comments

gcr

2 months ago

1 reply

Neat site!

This is a level lower than https://godbolt.org/ (the "Compiler Explorer") -- think of that site as turning C into assembly, and this site as watching the machine code actually run on virtual hardware.

iamcreasy

2 months ago

Is that the same as x86 emulation or there are subtle distinction?

FilosofumRex

2 months ago

1 reply

Is there GPU assembly (PTX) version available anywhere?

pjmlp

2 months ago

Kind of, there is

https://shader-playground.timjones.io/

Additionally you can select CUDA C++ or PTX on compiler explorer.

LarsDu88

2 months ago

3 replies

Is there a version of this for a simpler ISA like for the 6502 chip, the Gameboy chip, or straight up ARM?

soferio

2 months ago

1 reply

This is an assembler: https://paleotronic.com/merlinplus/

pjmlp

2 months ago

As info for others, the site currently has CORS errors, thus it doesn't assemble/execute.

enoent

2 months ago

For ARM (32-bit): https://alexaltea.github.io/unicorn.js/ or https://cpulator.01xz.net/

For other architectures, it feels like a missed opportunity to not have an independent WASM build of MAME's debugger, as the whole project could already be built in WASM (although I think the latest versions were broken, as that target isn't actively maintained): https://docs.mamedev.org/initialsetup/compilingmame.html#ems...

wkjagt

2 months ago

This one is quite fun: https://skilldrick.github.io/easy6502/

halb

2 months ago

1 reply

Nice to see my playground trending! All of this is essentially made possible by the blink engine by @jart: https://github.com/jart/blink/ Which is an x86-64-linux emulator written in a few kb of c code.

There is no Backend server, everything runs locally in the browser in a runtime that weights less than a screenshot of the website itself!

To implement it I modified the blink emulator to run as a C library, and compiled it into a Typescript + WASM module that exposes an emulator API. Then I built a regular web app on top of it.

philipallstar

2 months ago

Tiny nit! Spelling in your About section:

> Unlike traditional onlide editors

201984

2 months ago

1 reply

Pretty neat idea, but it evaluates the lzcnt instruction incorrectly, so it's possible others are wrong too. If you have access to a real x86_64 processor, you're probably better off just using it, and then you get the power of a full debugger with breakpoints in gdb.

Also, the "Guides" button and the "embed on your website" link on the main page are broken.

halb

2 months ago

This is mostly an educational tool, and it's intentionally designed to present data in a similar way to GDB. The idea is that students will use this tool to learn basic assembly concepts without the extra friction of GDB, and when they are ready they will move to the real tools, where hopefully they will already recognize some of the elements.

I am intentionally not implementing any useful feature beyond single stepping so that students will not remain stuck on a local minimum using this website.

Razengan

2 months ago

2 replies

I always wondered/wanted to play with a language that comes between Assembly and C (in terms of power/control, granularity, and also ease of use):

* Be just like Asm in every way, but:

* Have standardized architecture-agnostic mnemonics that translate to CPU-specific ones: like something that stands for both MOV on Intel and LDR on ARM.

* Take care of common boilerplate like function call rituals, or the multiple instructions required for loading 64-bit numbers on ARM.

Basically a real language like the ones in "programming simulation" games.

blashyrk

2 months ago

1 reply

Wouldn't that basically be very similar to, for example, LLVM IR?

halb

2 months ago

I was gonna say, this sounds exactly like LLVM IR, except for the ease of use

pjmlp

2 months ago

Besides LLVM IR, we have MSIL, WebAssembly, among many other bytecode formats, languages like Forth, or Lisp based assemblers.

osa1

2 months ago

1 reply

Is blink an interpreter for x86_64 instructions, or does it compile basic blocks to the host architecture?

I had a look at the source code but I'm not sure how it works. It looks a bit too small (50 kloc C + 6.6 kloc headers) to have code generators for all of the supported host architectures.

halb

2 months ago

It's an interpreter, but it does support JIT to x64 and arm. There are some details here: https://github.com/jart/blink/?tab=readme-ov-file#technical-...

On the x64-playground website it's just running as an interpreter, inside of web assembly

SilentM68

2 months ago

The Guides link does not work. Just stays at the same page.

runetech

2 months ago

Very nice and approachable! Almost makes me want to come back to assembly again ;-)

ngcc_hk

2 months ago