NetBeans delay when open project — Open Project dialog slow / freezes ~30 seconds (Windows fix)

Fix for: NetBeans is slow or freezes when opening a project, especially when the Open Project dialog takes about 30 seconds to appear.

If you searched for any of these, you are in the right place:

• netbeans delay when open project
• netbeans open project slow
• netbeans open project takes long time
• netbeans open project freezes / hangs / stuck
• netbeans file open project dialog slow
• netbeans 30 second delay open project
• netbeans waiting to open project
• netbeans freeze on open project windows
• apache netbeans open project lag
• netbeans project chooser slow oneDrive

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Quick answer (most common fix)

Problem: Click File → Open Project → NetBeans freezes ~30 seconds → then the folder chooser UI finally shows.

Cause: Module org.netbeans.swing.dirchooser uses Windows ShellFolder (Explorer/OneDrive). The UI thread blocks until that returns.

Fix: Disable the dirchooser module, restart NetBeans.

1-minute fix (PowerShell)

git clone https://github.com/Vlantoy/netbeans-open-project-dialog-slow.git
cd netbeans-open-project-dialog-slow
.\scripts\disable-dirchooser.ps1

Then File → Exit NetBeans completely, start again, try File → Open Project.

Manual fix (no clone)

Create this file (change 17 if your version is different):

%APPDATA%\NetBeans\17\config\Modules\org-netbeans-swing-dirchooser.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE module PUBLIC "-//NetBeans//DTD Module Status 1.0//EN"
                        "http://www.netbeans.org/dtds/module-status-1_0.dtd">
<module name="org.netbeans.swing.dirchooser">
    <param name="autoload">false</param>
    <param name="eager">false</param>
    <param name="enabled">false</param>
    <param name="jar">modules/org-netbeans-swing-dirchooser.jar</param>
    <param name="reloadable">false</param>
</module>

Restart NetBeans. The Open Project dialog should appear in 1–3 seconds, not 30.

Undo: run .\scripts\enable-dirchooser.ps1 or set enabled to true / delete the XML.

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Is this your bug? (symptom checklist)

Symptom	This fix
Delay happens before the Open Project window appears	Yes
Delay is roughly fixed ~20–40s (often exactly ~30s)	Yes
Windows Explorer itself is normal speed	Yes
Still slow with Wi‑Fi / network off	Yes
IDE looks frozen; mouse works outside NetBeans	Yes
Slow after you already picked a project (indexing/Maven)	No → see docs/other-causes.md

What people usually say

• “NetBeans delay when I open project”
• “Open Project freezes NetBeans for half a minute”
• “Nothing happens when I click Open Project, then suddenly the dialog appears”
• “NetBeans hangs only on File → Open Project”
• “Works fine until I open the project chooser”

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Why NetBeans is slow to open the project dialog

File → Open Project
        │
        ▼
createProjectChooser()     ← runs on UI thread (EDT)
        │
        ▼
JFileChooser + dirchooser
        │
        ▼
Windows ShellFolder  ← Explorer / OneDrive / icon overlays
        │
        ▼
~30 second hang → dialog finally paints

Apache NetBeans ships a note in the dirchooser module (MSG_SlownessNote):

Dialog seems to be slow, probably because of JDK bug.
Try upgrading JDK, remove zip files from Desktop, or run with
-J-Dnb.FileChooser.useShellFolder=false.

On many PCs (especially Windows 10/11 + OneDrive Desktop/Documents), that flag is not enough. Disabling dirchooser is the reliable fix.

Triggers that make “open project delay” worse

• Desktop or Documents redirected to OneDrive
• Many shell icon overlays (OneDrive, backup tools, etc.)
• Older/buggy JDK + ShellFolder interaction
• Large/messy Desktop (NetBeans even mentions zip files on Desktop)

What is usually NOT the cause (for this exact symptom)

• Slow HDD listing of NetBeansProjects (local list is often only a few ms)
• Proxy alone (hang often remains offline)
• Maven download (that is after you select a project)
• “Need to reinstall NetBeans” (reinstall rarely fixes ShellFolder hangs)

Full step-by-step debug: docs/debug-checklist.md

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Optional steps (if disable dirchooser is not enough)

1. JVM flag (Admin; may help, not always):

   -J-Dnb.FileChooser.useShellFolder=false
   

   Add to netbeans_default_options in netbeans\etc\netbeans.conf
   Helper: .\scripts\add-shellfolder-flag.ps1

2. Measure disk vs dialog: .\scripts\measure-fs.ps1

3. Thread dump while frozen: .\scripts\thread-dump-hint.ps1
   Look for AWT-EventQueue + ShellFolder / JFileChooser / dirchooser

4. Clean userdir test (does not delete your real settings):

   netbeans64.exe --userdir "$env:TEMP\nb-clean" --cachedir "$env:TEMP\nb-clean-cache"

5. Reinstall NetBeans without deleting %APPDATA%\Roaming\NetBeans
   (settings live there; wiping it is optional factory reset)

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Side effects of the fix

	Before	After disabling dirchooser
Open Project speed	Often ~30s freeze	Usually instant
Dialog look	Explorer-like	Plain Swing chooser
Projects, build, debug, Tomcat, JDK	Unchanged	Unchanged
Keymaps / IDE settings	Unchanged	Unchanged

You only change how the file/folder dialog is drawn, not your project code.

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Reinstall FAQ

Question	Answer
Will reinstall fix open-project delay?	Often no (same ShellFolder path)
Will reinstall delete my projects?	No (projects are your folders)
Will reinstall delete IDE settings?	No, unless you delete %APPDATA%\NetBeans

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Repo contents

Path	Purpose
scripts/disable-dirchooser.ps1	Main fix
scripts/enable-dirchooser.ps1	Revert
scripts/measure-fs.ps1	Prove disk is fast
scripts/add-shellfolder-flag.ps1	Optional conf flag
scripts/thread-dump-hint.ps1	Capture freeze stacks
docs/debug-checklist.md	Full debug order
docs/other-causes.md	Slow after open, Maven, index…

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Keywords (for search / SEO)

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Verified on

• Windows 11
• Apache NetBeans 17
• JDK 17
• OneDrive-backed Desktop/Documents
• Local project tree on D:\ listed in milliseconds; dialog still delayed ~30s until dirchooser disabled

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Contributing / “me too”

Open an Issue with:

• NetBeans version, JDK, Windows version
• OneDrive on Desktop/Documents? (yes/no)
• Which step fixed it (disable-dirchooser / shell flag / other)
• Optional: AWT-EventQueue lines from jcmd Thread.print during freeze

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License

MIT — see LICENSE.

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Tiếng Việt

Lỗi: NetBeans chậm / đơ khi mở project — bấm File → Open Project khoảng 30 giây mới hiện cửa sổ chọn folder.

Nguyên nhân: Module dirchooser gọi Windows ShellFolder (Explorer/OneDrive), block luồng UI.

Cách sửa: Tắt module org.netbeans.swing.dirchooser bằng script disable-dirchooser.ps1 hoặc file XML trong %APPDATA%\NetBeans\17\config\Modules\, rồi restart NetBeans.

Không mất project hay setting IDE. Dialog chọn folder chỉ đổi sang kiểu Swing đơn giản hơn.