Show HN: Wirebrowser – A JavaScript debugger with breakpoint-driven heap search

Posted by fcavallarin 19 hours ago

Hi HN!

I'm building a JavaScript debugger called Wirebrowser. It combines network inspection, request rewriting, heap snapshots, and live object search.

The main experimental feature is BDHS (Breakpoint-Driven Heap Search): it hooks into the JavaScript debugger and automatically captures a heap snapshot at every pause and performs a targeted search for the value or structure of interest. This reveals the moment a value appears in memory and the user-land function responsible for creating it.

Another interesting feature is the Live Object Search: it inspects runtime objects (not just snapshots), supports regex and object similarity, and lets you patch objects directly at runtime.

Whitepaper: https://fcavallarin.github.io/wirebrowser/BDHS-Origin-Trace

Feedback very welcome, especially on whether BDHS would help your debugging workflow.

Comments

Comment by klaushougesen1 3 hours ago

Great effort!, this stuff is hard to do - so applause for getting something shipped! popped an issue into you issues list.

I sometimes find these tools crash hard when pushed via large memory items, huge blobs of code, long base64 strings etc. Even chrome dev tools crash hard on large WS Messages.

Also perhaps post the video near the top instead of hiding it in the origin paper :), kids like videos these days.

https://www.youtube.com/watch?v=WA5nHk-6UJc

Comment by fcavallarin 1 hour ago

Thank you! And thanks for opening the issue - handling very large memory objects is definitely an area of improvement for Wirebrowser. It’s something I plan to harden as the tool matures.

Good point about the video ;) I’ll surface it more prominently, the whitepaper ended up a bit dense, so having the visual demo earlier probably helps a lot.

Comment by Sn0wCoder 2 hours ago

Only had a minute to install, build and use the app; but wow this is great! Thank you for building and showing us Wirebrowser. Are you building this because other tools do not meet your needs? I have not run across any tool(s) that combine all of these features into one package so hoping you all success with this release.

Comment by fcavallarin 55 minutes ago

Thanks! Yes - the motivation came from repeatedly switching between DevTools, Burp, and ad-hoc scripts whenever I needed to understand how an object ended up in the heap.

Wirebrowser started as an experiment to unify those workflows and make it possible to follow those values directly instead of stitching together multiple tools. It grew from the pain points I kept running into.

Comment by Veserv 1 hour ago

BDHS seems strictly less powerful than a time travel debugger. You can just set a hardware breakpoint and run backwards until the value is set.

Why not just do proper time travel? Is that absent for Javascript?

Comment by fcavallarin 23 minutes ago

Good point - in theory a full time-travel debugger is more powerful. The practical limitation is that time-travel for JavaScript usually requires instrumenting the code or running inside a custom record/replay environment. Today, JavaScript doesn’t expose any record/replay mechanism, access to hardware breakpoints, or the internal VM state needed to run execution backwards.

The browser’s debugging API (CDP) also doesn’t provide a way to capture or rewind engine state without modifying the application.

BDHS works within the constraints of zero instrumentation: it relies only on Debugger.paused and heap snapshots, so it can trace where a value originates without altering the code being debugged.

Comment by paulirish 2 hours ago

Very impressive to see the primitives of CDP be used for such a different DX than what's in existing devtools. Really well done.

Comment by fcavallarin 1 hour ago

Thanks a lot! It started as a small experiment with parts of CDP to solve some real-life debugging problems I kept running into, and it ended up opening workflows I hadn’t expected.