New standalone debugger in 0.83 way too slow / laggy

Description

The standalone debugger in latest RN 0.83 is way too slow / laggy which makes it impossible to debug.

Steps to reproduce

Simply create a new react native app (non-expo)
Try debug it by pressing j on terminal
It will open up the standalone debugger tool but then we have to wait a good 1-2minutes until its responsive
It's also slow in showing the logs whilst testing on a real device. Way slower than before

React Native Version

0.83.0

Output of `npx @react-native-community/cli info`

System:
  OS: macOS 15.6.1
  CPU: (14) x64 Apple M4 Pro
  Memory: 2.20 GB / 48.00 GB
  Shell:
    version: "5.9"
    path: /bin/zsh
Binaries:
  Node:
    version: 22.13.1
npm:
    version: 10.9.2
Managers:
  CocoaPods:
    version: 1.16.2
SDKs:
  iOS SDK:
    Platforms:
      - DriverKit 25.1
      - iOS 26.1
      - macOS 26.1
      - tvOS 26.1
      - visionOS 26.1
      - watchOS 26.1
  Android SDK: Not Found
Languages:
  Java:
    version: 17.0.10
Ruby:
    version: 3.2.2
npmPackages:
  "@react-native-community/cli":
    installed: 20.0.0
    wanted: 20.0.0
  react:
    installed: 19.2.0
    wanted: 19.2.0
  react-native:
    installed: 0.83.0
    wanted: 0.83.0
  react-native-macos: Not Found
npmGlobalPackages:
  "*react-native*": Not Found
Android:
  hermesEnabled: true
  newArchEnabled: true
iOS:
  hermesEnabled: true
  newArchEnabled: true

Screenshots and Videos

No response

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@alexkey89

Hello @alexkey89 , I have been testing the new debugger and have not experienced any lag.

Could you attach a reproducer and a video demonstrating the issue?

@migueldaipre

Ditto to what @migueldaipre said. Without more information we would have to close this one @alexkey89

@alexkey89

@alexkey89 I experience the same thing. It used to work well before we upgraded to react-native@0.83.0. Were you able to solve it?

@gituser8796

@gituser8796 unfortunately no. But there could be something related to reanimated from what I see. not sure if the warnings there are causing this lag.

@alexkey89

Exactly the same problem. The new debugger is too slow

demo.mov

@alexkey89 @gituser8796 @cortinico @migueldaipre

@cortinico

@cortinico any chance you guys will check it out? Once 0.83.x hits expo it might be affecting mode developer. At the moment we can't use the debugger :/

Any help would be appreciated.

@huntie

cc @huntie

@cortinico

@cortinico @huntie the 100% CPU happens only when the React Native DevTools window is in focus. I hope this helps

@husnaintahir

@husnaintahir @gituser8796

More info please

Need a reproducing app.
Can you think of any installed firewall, monitoring software, or other app sandboxing that might reduce networking/performance of a standalone Electron app on your system?

It looks like potentially you're dealing with a very large bundle (and therefore sourcemap), which will take time to be generated/parsed for the Sources panel in particular to work. The standalone RNDT desktop app should be giving the second part of this more memory headroom, rather than slowing down.

Investigation/workaround: Open debugger frontend in browser

Try pasting this URL into a Chromium-based browser. It will redirect and present React Native DevTools as a webpage (equivalent to the previous Chrome app window host).

http://localhost:8081/open-debugger

@huntie

@huntie thanks for looking into this one!

Need a reproducing app. [I don’t know how to reproduce it—see below.]
Can you think of any installed firewall, monitoring software, or other app sandboxing that might reduce networking or performance of a standalone Electron app on your system? [I don’t have any of these.]

Since the issue appeared, it has affected all apps, including older versions of React Native. Clearing Metro or any other cache I could think of did not resolve the issue.

It affects both “Hello World” apps and larger applications.

Visiting http://localhost:8081/open-debugger shows:
Cannot GET /open-debugger

+1 Debugger is very laggy (our codebase is large tho).

Sometimes debugger hangs (can't set/remove breakpoints), have to restart it.
Sometimes need to re-open it multiple times before it starts to be responsive (for example writing something in consode, clicking enter - does nothing - need to restart).

Looks to be more sivir on Android devices.

@huntie

@huntie @cortinico were you guys able to make some progress on this one? Thx!

@huntie

@huntie could you please let us know if there is a timeline for the fix?

@gituser8796

@gituser8796 Hey, we still have no way to repro this or understand why it's happening.

More thoughts maybe — can you confirm:

Which previous version of React Native you were comparing to, prior to 0.83?
@maksimlya mentioned "Looks to be more [severe] on Android devices". Could this be due to a slow physical Android device, or an Android emulator with little memory?

💡 Continuing the "is it Electron" investigation

Again, to try opening DevTools in a browser instead, could you try going to node_modules/@react-native/dev-middleware/dist/middleware/openDebuggerMiddleware.js and apply this patch to L43:

Dangerous test patch (unsupported)

- (experiments.enableOpenDebuggerRedirect && req.method === 'GET')
+ req.method === 'GET'

⬆️ This will enable /open-debugger in the browser. We don't recommend this — but this may help us narrow the investigation.

@huntie

@huntie I just applied the patch to openDebuggerMiddleware, and it works amazingly well. Thanks!

@gituser8796

@gituser8796 Thanks — in that case would you mind sending just the System: output of npx @react-native-community/cli info?

We've provisionally narrowed the impacted surface to the desktop app, but have no idea what's the root cause of this 🙏🏻

This issue is stale because it has been open for 180 days with no activity. It will be closed in 7 days unless you comment on it or remove the "Stale" label.

This issue is stale because it has been open 180 days with no activity. Remove stale label or comment or this will be closed in 7 days.

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New standalone debugger in 0.83 way too slow / laggy #54889

Description

Steps to reproduce

React Native Version

Output of `npx @react-native-community/cli info`

Screenshots and Videos

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New standalone debugger in 0.83 way too slow / laggy #54889

Description

Description

Steps to reproduce

React Native Version

Output of npx @react-native-community/cli info

Screenshots and Videos

Activity

react-native-bot commented on Dec 15, 2025

migueldaipre commented on Dec 15, 2025

cortinico commented on Dec 29, 2025

gituser8796 commented on Jan 9, 2026

alexkey89 commented on Jan 21, 2026

husnaintahir commented on Jan 22, 2026

gituser8796 commented on Jan 23, 2026

cortinico commented on Jan 23, 2026

gituser8796 commented on Jan 23, 2026

huntie commented on Jan 27, 2026

gituser8796 commented on Jan 27, 2026

maksimlya commented on Feb 8, 2026

gituser8796 commented on Feb 13, 2026

gituser8796 commented on Feb 19, 2026

huntie commented on Feb 19, 2026

gituser8796 commented on Feb 19, 2026

huntie commented on Feb 19, 2026

react-native-bot commented on Aug 19, 2026

react-native-bot commented on Aug 19, 2026

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Output of `npx @react-native-community/cli info`