How to fix "JavaScript error occurred in the main process" error?

"A JavaScript error occurred in the main process" is a box from an app built on Electron, such as Discord, Slack, an old Teams or a game launcher: the app's own start-up code failed. Windows and macOS are almost never the cause. Close every copy of the app, then clear its data folder and reinstall it from the maker.

Facts checked on 15 October 2026. Steps written for Windows 11 (25H2 and 26H2) and Windows 10 22H2, with the macOS steps for Mac users.

What "A JavaScript error occurred in the main process" means

Discord, Slack, the old Microsoft Teams, many code editors and some game launchers are built on Electron, a framework that runs a web app on your desktop. Each Electron app has one main process, the part that starts the app, opens its windows and updates it.

We read Electron's own start-up code. When an error in that main process is not handled by the app, Electron catches it, writes Uncaught Exception: in front of the error details and shows them in a box titled A JavaScript error occurred in the main process. The same code says it does not quit on such an error, so the app can hang on after you click OK.

How to read the error box and find the program behind it

Press Win + Shift + S on Windows or Cmd + Shift + 4 on a Mac and capture the whole box. Then look at three things: the title, the first Error: line and the paths in the at lines. The paths name the program, even when the box itself does not.

What causes the JavaScript error in the main process, from most to least common

Most often the app's own files or settings are damaged, usually by an update that did not finish or a PC that shut down during one. Less often a second copy of the app is still running, the app is an old version that no longer works, or it lacks permission to its folder. Rarely, malware or other software is behind it.

Windows updates and macOS updates do not cause this box directly. They can only matter when they stop an app update half way, which is the damaged files case above.

How to fix "A JavaScript error occurred in the main process"

Fixes 1 to 3 work for any Electron app and clear most cases. Fix 4 is for Teams, Fix 5 for permission errors and Fix 6 for Mac users. Fixes 7 and 8 are for when the box keeps coming back after a clean reinstall.

Fix 1. Close every copy of the app and start it again

2 minutesNo riskEveryone first, especially when the box appeared right after an update.

Electron apps keep running in the notification area after you close the window, and they update their own files at start-up. If an old copy is still running, the update and the start-up collide. Electron also keeps the app open after the error, so a broken copy can linger.

1. Take a picture of the box, then click OK.
2. Open the hidden icons arrow in the notification area. If the app's icon is there, right-click it and choose Quit or Exit.
3. Press Ctrl + Shift + Esc to open Task Manager and select Processes.
4. Find every entry of the app, under Apps and under Background processes. Select each one and choose End task.
5. Restart the PC so any stuck updater is gone too.
6. Open the app once from the Start menu and wait until its update screen finishes.

Step by step with Task Manager: Close a frozen app (Task Manager, Force Quit).

Fix 2. Delete the app's data folder so it rebuilds its cache and settings

5 minutesLow riskThe box comes back on every start, or names a settings or JSON file.

Electron apps keep their cache and settings in a folder under your user profile, separate from the program. A damaged file there stops start-up each time. Microsoft gives this exact step for the Teams desktop app: quit Teams, delete its cache folder, start again.

1. Close every copy of the app as in Fix 1.
2. Press Win + R, type the line below and press Enter. Most Electron apps keep their data here.

   %appdata%

3. Find the folder with the app's name, for example discord or Slack. Microsoft's classic Teams used %appdata%\Microsoft\Teams.
4. Rename the folder by adding .old to its name. Renaming keeps a way back; delete it later once the app works.
5. Start the app, sign in and wait until it has rebuilt its data.

Using the new Teams? Microsoft's steps are to reset the app in Settings > Apps > Installed apps, or to delete %userprofile%\appdata\local\Packages\MSTeams_8wekyb3d8bbwe\LocalCache\Microsoft\MSTeams. For Discord, see our Discord fatal JavaScript error guide, which names both of its folders.

Fix 3. Uninstall the app, remove its leftovers and install a fresh copy from the maker

15 minutesLow riskThe box names a missing module, a missing file or a file that is not a valid Win32 application.

Many Electron apps install per user into %LocalAppData% and keep data in %AppData%. A normal uninstall can leave both behind, so a new install loads the same damaged files. Removing them first makes the reinstall really fresh.

1. Close every copy of the app as in Fix 1.
2. Windows 11: open Settings > Apps > Installed apps, select the ... next to the app and choose Uninstall. Windows 10: Settings > Apps > Apps & features.
3. Press Win + R, type this and press Enter. Delete the app's folder if it is still there.

   %localappdata%

4. Press Win + R again, open %appdata% and delete the app's folder there too, or the .old copy from Fix 2.
5. Restart the PC.
6. Download the installer from the maker's own site or the Microsoft Store, never from a download portal, and install it with a normal double-click.

Step by step for Windows 11 and 10: Uninstall a program or app in Windows.

Fix 4. Replace classic Microsoft Teams with the new Teams

15 minutesLow riskThe paths in the box point to a Microsoft Teams folder.

Microsoft ended support for classic Teams on 1 July 2024 and its availability on 1 July 2025: after that date the classic client no longer works. Reinstalling classic Teams brings the same broken client back, which is why the reader's Mac reinstall did not help.

1. Quit Teams: right-click its icon on the taskbar and select Quit.
2. In Settings > Apps > Installed apps, uninstall Microsoft Teams classic and any Teams Machine-Wide Installer entry.
3. Install the new Microsoft Teams from Microsoft's Teams download page or the Microsoft Store.
4. Start the new Teams and sign in with your work, school or personal account.
5. If the new Teams misbehaves, reset it: Installed apps, the ... next to Microsoft Teams, Advanced options, then Reset.
6. No permission to install apps on a work PC? Use Teams on the web in a supported browser and ask your IT department.

Reset deletes the app's local data, including your personal settings. General steps: How to repair or reset an app in Windows.

Fix 5. Test the app once as administrator when the box says EACCES or EPERM

5 minutesLow riskThe Error line says EACCES, EPERM, permission denied or operation not permitted.

EACCES: permission denied means the app may not create or change a file in its own folder. One run as administrator shows whether permissions are the block. It is a test, not a fix to keep.

1. Close every copy of the app as in Fix 1.
2. Type the app's name in the Start menu, right-click it and choose Run as administrator.
3. Select Yes in User Account Control.
4. If the app now opens, close it and do Fix 3 while signed in to your normal account, so the new folders belong to you.
5. Do not set the app to always run as administrator.

How to run a program as administrator once: How to run a program as administrator or in compatibility mode. If the app was ever installed or started as administrator or for all users, its folders may belong to another account, which the clean reinstall in Fix 3 resets.

Fix 6. Fix the error on a Mac: remove the app's data and install the right build

10 minutesLow riskYou see the box on a Mac, for example with Teams or Slack.

On a Mac, Electron apps keep their data in your Library folder, and dragging the app to the Trash leaves it behind. A reinstall then loads the same damaged data. Checking the build also catches an app made for another kind of Mac.

1. Quit the app: right-click its icon in the Dock and select Quit, or press Cmd + Q.
2. In Finder, press Cmd + Shift + G and open ~/Library/Application Support. Move the folder with the app's name to the Trash.
3. For Teams, Microsoft's paths are ~/Library/Application Support/Microsoft/Teams for classic Teams, and ~/Library/Group Containers/UBF8T346G9.com.microsoft.teams and ~/Library/Containers/com.microsoft.teams2 for the new Teams.
4. Open the Apple menu, About This Mac, then System Report. On newer macOS, select More Info first.
5. Under Software, select Applications, find the app and read its Kind line to see which build is installed.
6. Delete the app and install the current version from the App Store or the maker's site.

Fix 7. Scan for malware when the box names files you never installed

20 minutesLow riskThe at lines name a file, mod or folder you do not recognize.

Some malware and client mods work by changing an Electron app's start-up code. When the changed code breaks, the app ends in this box. A reinstall alone does not help if the malware writes its code back.

1. Write down every name in the at lines that is not the app's own folder.
2. If you installed a mod or theme yourself, remove it, then do Fix 3.
3. If you did not, run a full scan and then a Microsoft Defender Offline scan: How to scan for malware with Microsoft Defender.
4. When the scan is clean, do the clean reinstall in Fix 3.
5. From a phone or another device you trust, change the app's password and turn on two-factor sign-in.

Fix 8. Find conflicting software with a clean boot

20 minutesLow riskThe box returns even after a clean reinstall and a clean scan.

Overlays, game boosters and some security suites load into other programs. A clean boot starts Windows with Microsoft services only, so if the app opens then, one of the switched-off programs is the cause.

1. Open System Configuration. Select Search on the taskbar, type msconfig and select System Configuration from the results.
2. Hide Microsoft services. On the Services tab, select the Hide all Microsoft services check box. Only services from other companies stay in the list.
3. Disable the remaining services. Select Disable all, then select Apply.
4. Open Task Manager. On the Startup tab of System Configuration, select Open Task Manager.
5. Disable the startup apps. On the Startup apps tab in Task Manager, select each item whose status is Enabled and select Disable. Write down or take a screenshot of the items you disable: you need the list to turn them back on.
6. Confirm the changes. Close Task Manager. On the Startup tab of System Configuration, select OK.
7. Restart and test. Restart the PC. Windows now starts in a clean boot environment: try again the thing that failed (run the app, install the update, uninstall the program).

These steps were written for Windows 11 25H2 and 26H2. The full page with the other versions and what each result means: How to perform a clean boot in Windows

When the app opens in the clean boot, turn services back on in small groups and restart each time. The group that brings the box back holds the program to update or remove.

Still getting the JavaScript error in the main process? What to collect and send

If the box survives a clean reinstall, the app's maker has to look at it. A complete report saves a round of questions.

• The whole box: your picture of the title, the Error: line and every at line.
• The app and its version, from Installed apps on Windows or the Kind and Version lines in System Report on a Mac.
• Your system: press Win + R, type winver and press Enter, or open About This Mac.
• When it appears: at start-up, after an update, or when you close the app.
• What you tried, in order, including Fixes 1 to 3.

How to keep the JavaScript error from coming back

If you need the app right away while you fix the desktop version, most of these apps have a web version, such as Teams on the web or Discord in the browser. They use the same account and do not depend on the files on your PC.

Frequently asked questions

Is "A JavaScript error occurred in the main process" a virus?

Usually not. The box is Electron's standard message for an error that the app's code did not handle, and the usual reasons are damaged app files or a copy of the app still running. Malware is a rare cause: some malware changes an Electron app's start-up code, and a broken change ends in this box. Look at the at lines. If they name only the app's own folders, follow Fixes 1 to 3. If they name files you never installed, scan first (Fix 7).

Is this a Windows 10 or Windows 11 problem?

No. The box looks the same on Windows 11, Windows 10 and macOS, because it comes from the app, not from the operating system. The fixes are the same on both Windows versions; only the Settings menu names differ, and the steps give both. Windows matters only when it blocks the app's folder, which shows as EACCES or EPERM in the box (Fix 5). Windows 10 left Microsoft support on 14 October 2025, so newer app versions may drop it over time.

Why do I get the same error on a Mac?

The apps that show it, such as Slack, Discord and the old Teams, run the same Electron code on Windows and macOS. So the same title appears on both, with Mac paths such as /Applications/Slack.app in the at lines. The fix is the same idea: quit the app, remove its folder in ~/Library/Application Support, and install the current version. For Teams on a Mac, Microsoft's own paths are in Fix 6, and classic Teams no longer works at all.

Does this error mean Java is broken on my PC?

No. JavaScript and Java are two different languages that only share part of a name. Electron apps run JavaScript inside the app itself, so you do not need to install, update or remove Java, and doing so changes nothing. Searches such as "java script error occurred in the main process" or "java error occurred in the main process" all mean the same Electron box. Check the box's paths to see which app showed it, and start with Fix 1.

What should I do if Valorant, League of Legends or the Riot Client shows this error?

The title is Electron's fixed text, so the box comes from a launcher window built on it, not from the game itself. Close every Riot process in Task Manager and restart the PC (Fix 1). If it returns, uninstall the launcher in Installed apps, delete its leftover folder that the at lines point to, and install it again from Riot's own site (Fix 3). We could not confirm Riot's folder layout for this page, so follow the paths in your box.

Cursor, DMM Game Player or another app shows the box. Do the same fixes work?

Yes, as long as the box has this exact title, because then the app runs on Electron. The at lines tell you where its files are, usually under %LocalAppData% and %AppData% on Windows or ~/Library/Application Support on a Mac. Close every copy, rename its data folder, then reinstall from the maker's site (Fixes 1 to 3). Code editors also load extensions at start-up, so if the paths name an extension, remove that extension first.

Will I lose my chats or files if I delete the app's data folder?

Not for apps that keep your data online, such as Teams, Slack and Discord. Their chats, servers, channels and files live on your account and come back when you sign in. You lose local things: the sign-in on this PC, start-up and window settings, and sometimes downloaded media in the cache. Apps that keep work only on your PC, such as some editors, may also store unsaved data there. That is why Fix 2 renames the folder instead of deleting it.

What does "Uncaught Exception" mean in this error?

It means an error happened in the app's main process and none of the app's code was written to handle it. Electron then catches it as a last safety net and shows the box. Everything after Uncaught Exception: is the stack trace: first the error itself, then the at lines that list the functions and files that were running. Read the first line to learn the reason and the paths to learn which app and folder are involved.

Can I click OK and keep using the app?

Sometimes. Electron's code shows the box without quitting the app, so it can keep running after you click OK, especially when the error appeared while closing a window. But the part that failed is not working, so the app may hang, lose settings or not update. If the box appeared once, restart the app cleanly (Fix 1). If it appears again, do not ignore it: clear the data folder and reinstall (Fixes 2 and 3).

I still use Windows 7. Can I fix the error there?

Probably not for long. Windows 7 has been out of support for years, and current versions of many Electron apps no longer install on it. Discord, for example, dropped Windows 7, 8 and 8.1 in March 2024. On an old app version the error can come from a bug that was only fixed in versions your Windows cannot run. Try Fixes 1 to 3 once. If that fails, use the app's web version in a browser or move to a supported Windows.