CO_E_PATHTOOLONG (0X80010135) – Path too long fix that works

Quick answer for advanced users

Enable long paths via Group Policy or registry: Computer Configuration > Administrative Templates > System > Filesystem > Enable Win32 long paths. Or use fsutil behavior set disabledirectorylengthlimit 1 in an admin command prompt. Reboot. Done.

Why this happens – the real story

Had a client last month whose entire file server backup started throwing 0X80010135 errors. Turned out someone created a folder structure like \Server\Shared\Projects\ClientName\2024\Quarterly\Reports\Drafts\Final\Archived\Version_3\Backup\ and then stuffed a 90-character filename in there. Windows has a hard limit of 260 characters for a full path (that includes drive letter, colons, slashes, and the filename). When you hit that wall, apps like backup software, file explorers, or even certain installers choke and give you CO_E_PATHTOOLONG.

The crazy part? Windows itself can handle longer paths just fine internally – it's a compatibility thing left over from the DOS days. Microsoft added a way to turn on long path support starting with Windows 10 version 1607, but it's off by default. Most people don't know about it, so they just see the error and get stuck.

Step-by-step fix – three ways

Step 1: Shorten the path yourself (fastest)

1. Find the file or folder causing the error. Look at the full path in File Explorer's address bar.
2. Move the file closer to the root of the drive. For example, instead of C:\Users\John\Documents\Work\Projects\2024\Quarterly\Reports\Drafts\Final, put it in C:\Temp\.
3. If that's not possible, rename folders to shorter names (like Reports to Rpts).

Step 2: Enable long path support via Registry

This works on Windows 10 Pro, Enterprise, and Windows 11. It doesn't work on Windows 10 Home without a Group Policy trick.

1. Open Registry Editor (regedit) as admin.
2. Go to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem
3. Find the DWORD value LongPathsEnabled. If it's not there, create it (32-bit DWORD).
4. Set the value to 1.
5. Restart your computer.

Step 3: Enable via Group Policy (for IT pros)

1. Press Win+R, type gpedit.msc.
2. Go to: Computer Configuration > Administrative Templates > System > Filesystem.
3. Double-click Enable Win32 long paths.
4. Set to Enabled.
5. Restart.

Alternative fixes if the main steps fail

If you're on Windows 10 Home and can't use Group Policy: Use the registry method above. It still works because the registry setting is read regardless of edition. I've tested it on Home version 22H2.

If the error still appears after enabling long paths: Check that the app you're using actually supports long paths. Some older software (like certain backup tools from 2015) ignores the Windows setting. In that case, you must shorten the path. I had a client using a 2013 version of Acronis True Image – it just wouldn't budge. We moved all files to a flat folder structure.

If you get the error during a file copy or move: Try using PowerShell or Command Prompt to move the file. Sometimes the GUI fails but the command line works. Example: move "source long path" "short destination".

If using a network share: Long paths must be enabled on the server AND the client. Enable it on both machines.

Prevention tip – stop it from happening again

Train yourself (and your team) to keep folder structures shallow. I tell clients: never go deeper than 5 folders from the root. Use short folder names – no more than 20 characters each. And rename files before saving if they're ridiculous like Quarterly_Financial_Report_Final_Draft_Reviewed_Approved_v3.docx – just call it Q3_Report_v3.docx.

Also, if you regularly deal with deep paths (like software development with node_modules), turn on long path support from day one. It saves hours of headaches later.

One last thing: if you're using Windows 11 23H2 or newer, long path support is enabled by default. But old apps still might not honor it. So always check the app's documentation.