I am using arduino ide on win11, it used to work well, but today I can't open it.
PS D:\01-install\arduino\Arduino IDE> & ".\Arduino IDE"
PS D:\01-install\arduino\Arduino IDE>
Arduino IDE 2.3.9
Checking for frontend application configuration customizations. Module path: D:\01-install\arduino\Arduino IDE\resources\app\lib\backend\electron-main.js, destination 'package.json': D:\01-install\arduino\Arduino IDE\resources\app\package.json
Setting 'theia.frontend.config.appVersion' application configuration value to: "2.3.9" (type of string)
Setting 'theia.frontend.config.cliVersion' application configuration value to: "1.5.0" (type of string)
Setting 'theia.frontend.config.buildDate' application configuration value to: "2026-05-26T13:59:51.973Z" (type of string)
Frontend application configuration after modifications: {"applicationName":"Arduino IDE","defaultTheme":{"light":"arduino-theme","dark":"arduino-theme-dark"},"defaultIconTheme":"none","electron":{"windowOptions":{},"showWindowEarly":true,"splashScreenOptions":{},"uriScheme":"arduino-ide"},"defaultLocale":"","validatePreferencesSchema":false,"reloadOnReconnect":true,"uriScheme":"theia","preferences":{"window.title":"${rootName}${activeEditorShort}${appName}","files.autoSave":"afterDelay","editor.minimap.enabled":false,"editor.tabSize":2,"editor.scrollBeyondLastLine":false,"editor.quickSuggestions":{"other":false,"comments":false,"strings":false},"editor.maxTokenizationLineLength":500,"editor.bracketPairColorization.enabled":false,"breadcrumbs.enabled":false,"workbench.tree.renderIndentGuides":"none","explorer.compactFolders":false},"appVersion":"2.3.9","cliVersion":"1.5.0","buildDate":"2026-05-26T13:59:51.973Z"}
Starting backend process. PID: 21396
Showing main window early
Using browser-only version of superagent in non-browser environment
Configuration directory URI: 'file:///c%3A/Users/18826/.arduinoIDE'
Configuring to accept webviews on '^.+\.webview\..+$' hostname.
2026-05-27T14:46:49.855Z root INFO Backend u.initialize: 18.6 ms [Finished 0.421 s after backend start]
2026-05-27T14:46:49.856Z root INFO Backend Object.initialize: 17.4 ms [Finished 0.421 s after backend start]
2026-05-27T14:46:49.856Z root INFO Backend a.initialize: 1.2 ms [Finished 0.421 s after backend start]
2026-05-27T14:46:49.856Z root INFO Backend a.initialize: 1.0 ms [Finished 0.421 s after backend start]
2026-05-27T14:46:49.856Z root INFO Backend u.initialize: 1.2 ms [Finished 0.422 s after backend start]
2026-05-27T14:46:49.858Z root INFO Backend l.initialize: 18.4 ms [Finished 0.422 s after backend start]
2026-05-27T14:46:49.863Z root INFO configured all backend app contributions
2026-05-27T14:46:49.863Z root INFO Backend l.onStart: 0.9 ms [Finished 0.430 s after backend start]
2026-05-27T14:46:49.864Z root INFO Backend d.onStart: 0.2 ms [Finished 0.430 s after backend start]
2026-05-27T14:46:49.864Z root INFO Backend a.onStart: 0.4 ms [Finished 0.431 s after backend start]
2026-05-27T14:46:49.865Z config INFO >>> Initializing CLI configuration...
2026-05-27T14:46:49.865Z root INFO Backend x.onStart: 0.6 ms [Finished 0.432 s after backend start]
2026-05-27T14:46:49.865Z config INFO Loading CLI configuration from c:\Users\18826\.arduinoIDE\arduino-cli.yaml...
2026-05-27T14:46:49.865Z daemon INFO Starting daemon from D:\01-install\arduino\Arduino IDE\resources\app\lib\backend\resources\arduino-cli.exe...
2026-05-27T14:46:49.865Z root INFO Backend w.onStart: 0.3 ms [Finished 0.432 s after backend start]
2026-05-27T14:46:49.865Z discovery-log INFO start
2026-05-27T14:46:49.865Z discovery-log INFO start new deferred
2026-05-27T14:46:49.865Z root INFO Backend v.onStart: 0.2 ms [Finished 0.432 s after backend start]
2026-05-27T14:46:49.865Z root INFO Backend a.onStart: 0.1 ms [Finished 0.433 s after backend start]
2026-05-27T14:46:49.875Z root INFO Theia app listening on http://127.0.0.1:62218.
2026-05-27T14:46:49.875Z root INFO Finished starting backend application: 10.5 ms [Finished 0.443 s after backend start]
2026-05-27T14:46:49.876Z root WARN The local plugin referenced by local-dir:/c%3A/Users/18826/.arduinoIDE/plugins does not exist.
2026-05-27T14:46:49.876Z root WARN The local plugin referenced by local-dir:/c%3A/Users/18826/.arduinoIDE/deployedPlugins does not exist.
2026-05-27T14:46:49.876Z root WARN The local plugin referenced by local-dir:C:\Users\18826\.arduinoIDE\plugins does not exist.
2026-05-27T14:46:49.887Z config INFO Loaded CLI configuration: {"board_manager":{"additional_urls":[]}}
2026-05-27T14:46:49.887Z config INFO Loading fallback CLI configuration to get 'directories.data' and 'directories.user'
2026-05-27T14:46:49.918Z root INFO Resolve plugins list: 52.0 ms [Finished 0.486 s after backend start]
2026-05-27T14:46:50.003Z daemon INFO time="2026-05-27T22:46:49+08:00" level=info msg="arduino-cli version 1.5.0"
2026-05-27T14:46:50.006Z daemon INFO time="2026-05-27T22:46:50+08:00" level=info msg="Using config file: c:\\Users\\18826\\.arduinoIDE\\arduino-cli.yaml"
time="2026-05-27T22:46:50+08:00" level=info msg="Executing `arduino-cli daemon`"
2026-05-27T14:46:50.017Z daemon INFO Daemon is now listening on 127.0.0.1:62219
{"IP":"127.0.0.1","Port":"62219"}
2026-05-27T14:46:50.017Z daemon INFO Daemon is running.
2026-05-27T14:46:50.023Z config INFO Loaded fallback CLI configuration: {"directories":{"user":"C:\\Users\\18826\\Documents\\Arduino","data":"C:\\Users\\18826\\AppData\\Local\\Arduino15"}}
2026-05-27T14:46:50.023Z config INFO Merged CLI configuration with the fallback: {"directories":{"user":"C:\\Users\\18826\\Documents\\Arduino","data":"C:\\Users\\18826\\AppData\\Local\\Arduino15"},"board_manager":{"additional_urls":[]}}
2026-05-27T14:46:50.023Z config INFO Loaded the CLI configuration.
2026-05-27T14:46:50.028Z root ERROR Uncaught Exception: Error: 14 UNAVAILABLE: No connection established. Last error: read ECONNRESET (2026-05-27T14:46:50.026Z)
2026-05-27T14:46:50.028Z root ERROR Error: 14 UNAVAILABLE: No connection established. Last error: read ECONNRESET (2026-05-27T14:46:50.026Z)
at t.callErrorFromStatus (D:\01-install\arduino\Arduino IDE\resources\app\lib\backend\main.js:2:3120831)
at Object.onReceiveStatus (D:\01-install\arduino\Arduino IDE\resources\app\lib\backend\main.js:2:6722925)
at Object.onReceiveStatus (D:\01-install\arduino\Arduino IDE\resources\app\lib\backend\main.js:2:2604592)
at Object.onReceiveStatus (D:\01-install\arduino\Arduino IDE\resources\app\lib\backend\main.js:2:2604037)
at D:\01-install\arduino\Arduino IDE\resources\app\lib\backend\main.js:2:4353025
at process.processTicksAndRejections (node:internal/process/task_queues:77:11)
for call at
at s.makeUnaryRequest (D:\01-install\arduino\Arduino IDE\resources\app\lib\backend\main.js:2:6722456)
at s.create (D:\01-install\arduino\Arduino IDE\resources\app\lib\backend\main.js:2:3119924)
at instance (D:\01-install\arduino\Arduino IDE\resources\app\lib\backend\main.js:2:6328633)
at new Promise (<anonymous>)
at y.createClient (D:\01-install\arduino\Arduino IDE\resources\app\lib\backend\main.js:2:6328610)
at y.create (D:\01-install\arduino\Arduino IDE\resources\app\lib\backend\main.js:2:6327518)
at D:\01-install\arduino\Arduino IDE\resources\app\lib\backend\main.js:2:6326414
at D:\01-install\arduino\Arduino IDE\resources\app\lib\backend\main.js:2:1050849
at s.invoke (D:\01-install\arduino\Arduino IDE\resources\app\lib\backend\main.js:2:1050939)
at a.fire (D:\01-install\arduino\Arduino IDE\resources\app\lib\backend\main.js:2:1052742)
2026-05-27T14:46:50.030Z config INFO Mapped the CLI configuration: {"dataDirUri":"file:///c%3A/Users/18826/AppData/Local/Arduino15","sketchDirUri":"file:///c%3A/Users/18826/Documents/Arduino","additionalUrls":[],"network":"none","locale":"en"}
2026-05-27T14:46:50.030Z config INFO Validating the CLI configuration...
2026-05-27T14:46:50.032Z config INFO The CLI config is valid.
2026-05-27T14:46:50.032Z config INFO <<< Initialized the CLI configuration.
2026-05-27T14:46:50.319Z root INFO Deploy plugins list: 453.2 ms [Finished 0.887 s after backend start]
2026-05-27T14:46:50.860Z root INFO creating connection for 1
2026-05-27T14:46:51.589Z root WARN A command editor.action.toggleStickyScroll is already registered.
Opening channel for service path '/services/electron-window'.
Opening channel for service path '/services/ide-updater'.
2026-05-27T14:46:51.669Z root INFO Start frontend contributions: 189.6 ms [Finished 1.777 s after frontend start]
2026-05-27T14:46:51.669Z root INFO Changed application state from 'init' to 'started_contributions'.
2026-05-27T14:46:51.678Z root INFO Changed application state from 'started_contributions' to 'attached_shell'.
2026-05-27T14:46:51.678Z root INFO >>> Restoring the layout state...
2026-05-27T14:46:51.844Z root INFO [82c4b840-508e-482c-8d7f-20b3aa5b900e] Waiting for backend deployment: 57.9 ms [Finished 1.832 s after frontend start]
2026-05-27T14:46:52.136Z root INFO [hosted-plugin: 7864] PLUGIN_HOST(7864) starting instance
[Object: null prototype] {}
2026-05-27T14:46:52.610Z root INFO [82c4b840-508e-482c-8d7f-20b3aa5b900e] Sync of 23 plugins: 896.0 ms [Finished 2.728 s after frontend start]
Hi @junwenl. Arduino IDE communicates with some of its helper tools via an internal TCP/IP port in your computer on "localhost". This communication is failing somehow. These failures are usually found to be caused by "external" interference or misconfiguration. By "external", I mean that it is something separate from the Arduino IDE application, its helper tools, or their configuration. Examples would be your antivirus software, firewall, network configuration including the use of a proxy or VPN.
Is there anything notable about your system that might be relevant?
I'm going to ask you to provide the logs produced by Arduino IDE when some additional debugging output is enabled. It is possible those will provide some clue that will allow us to understand the cause of the problem.
This procedure is not intended to solve the problem. The purpose is to gather more information.
Open the Arduino IDE installation folder (D:\01-install\arduino\Arduino IDE).
In the folder listing of the Arduino IDE installation folder, hold the Shift key while clicking the right hand button on the mouse.
A context menu will open.
Select "Open PowerShell window here" from the menu.
PowerShell will now open with the current directory set to the Arduino IDE installation folder.
Type the following command in the PowerShell window:
$Env:GRPC_VERBOSITY = "DEBUG"
Press the Enter key.
Type the following command in the PowerShell window:
$Env:GRPC_TRACE = "all"
Press the Enter key.
Type the following command in the PowerShell window:
& ".\Arduino IDE"
Press the Enter key.
Debug output should now be printed to the PowerShell window as Arduino IDE starts (or fails to start).
Wait for Arduino IDE to .
Switch back to the PowerShell window if the Arduino IDE window took the focus.
Press the Ctrl+Shift+A keyboard shortcut.
This will select all the text in the PowerShell window.
Press the Ctrl+C keyboard shortcut.
This will copy the contents of the PowerShell window to the clipboard.
Open a reply here on this forum topic by clicking the "Reply" button.
Click the <CODE/> icon on the post composer toolbar.
This will add the forum's code block markup (```) to your reply to make sure the error messages are correctly formatted.
The hang on startup caused by ungraceful handling of invalid proxy configuration specified by these environment variables is tracked here:
And here a report of the inappropriate usage of the configuration in the case where it is valid:
I haven't reproduced the latter one, as my few experiments with configuring the proxy via these variables were successful. However, it does seem like it might have been the case here, as my interpretation of the cryptic information from the logs is that this was a failure to connect to the "backend" via localhost, rather than a failure to access the Internet.
There is a related request here:
At the minimum, that would provide more user friendly access to the logs that provide valuable clues as to which of the many diverse system problems might have caused the hang on startup.
Ideally, Arduino IDE would also display a message that provides a human friendly explanation of the situation.
There is a related issue here:
(but that wouldn't help in the more rare case where Arduino IDE doesn't even manage to initiate communication with Arduino CLI)
This procedure is not intended to solve the problem. The purpose is to gather more information.
