Find the files that will not copy: list long paths and invalid names

You are about to move a folder to a backup disk or a shared cloud folder, and the copy stops with "could not copy" and does not say which file. The cause is usually a path that is too long, a character a file name cannot hold, or a name that ends with a space or a period. Finding them by hand in a folder of thousands of files takes hours. Path and Filename Checker by Hullspark, a Windows app, lists the files and folders that have a problem once you choose the folder. The free edition shows the first 50 rows of the list.

Hullspark · 2026-10-23

Checking by hand

Turning on the Windows "long paths" setting (the registry value LongPathsEnabled) does not by itself make a copy succeed. Microsoft's documentation says the setting takes effect only for an app that declares it supports long paths＊1. If the program you copy with does not, the limit of 260 stays.

robocopy in a command prompt supports paths longer than 256 characters by default＊2. Copy with something like robocopy source destination /E /LOG:robocopy.log; failed items are in the log, and an exit code of 8 or more means at least one failed＊2. This is a real copy, though, and you read the log to find which file has which problem. If you want the list of problems before you copy, that is what this app is for.

What it finds

A path at or over the limit you set (260 to begin with; any number from 20 up)
A single name longer than 255 characters
Characters that cannot be used in a name (\ / : * ? " < > | and control characters), including the private-use characters that a Mac share or WSL stores in their place
Reserved names such as CON, NUL, COM1 and LPT1
A name that ends with a space or a period, or starts with a space
Two names in the same folder that differ only in upper and lower case

One row can carry several kinds. Press Check: the count of problems is split by kind, and the table shows where each item is, its length now, its length after the move and how many characters it is over. Up to 259 characters pass and from 260 they fail. For a folder it is 247 (with the default limit).

(Full edition) Enter the destination to see the length after the move

A path gets longer when it moves, because the destination folder's name goes in front of it. Enter the destination and the table shows the length after the move, so you see which items will fail there before you copy anything. The app counts characters of the full path and does not know the rules of any particular storage place; you set the limit that matches yours. In the free edition there is no destination box, so the length after the move in the table is the same as the length now.

Free and full edition

The free edition is the full check: every problem is counted by kind, and the list shows the first 50 rows. The full edition is a one-time add-on bought through the Microsoft Store, from a button in the app. It adds every row of the list, CSV export, the destination folder, the wider list of characters (# % & { } ~), and renaming of selected rows.

When it renames, it replaces unusable characters with the full-width look-alike (or an underscore where there is none), removes leading spaces and trailing spaces and periods, adds an underscore to a reserved name, shortens a name that is too long (the extension stays) and numbers names that would clash. You see the old and new name side by side, confirm, and only the selected rows are renamed. Nothing is overwritten. Each rename is written to a history file at once, and Undo puts the names back. Undo works in the free edition too.

Your data

Checking never changes a file. The app reads names only; it does not open files or read what is inside them, and file names and contents are never sent anywhere. The only network use is the Microsoft Store, for checking and adding the full edition. It stores only its settings and a record of renames, on this PC. Details are in the privacy policy.

What it cannot do

It does not claim to find every problem; what was tested is a made-up folder. Network drives and permission problems were not tested. Folders it cannot read are counted and named, and the check goes on. Folders that are links to other folders are not entered. Renaming can break links from other files and shortcuts.

Coming to the Microsoft Store

FAQ

If I set the limit to 260, does a 260-character path pass?

No. The app lists paths of 260 characters or more. The standard Windows limit of 260 counts the closing NUL, the mark that ends the string, so 259 characters pass. Enter the limit that matches your storage place; the app does not know the rules of any particular one.

Does checking change any file?

No. The app reads file and folder names only; it does not open files or read what is inside them. Names are changed only in the full edition, for the rows you select and confirm.

Can I undo a rename?

Yes. Each rename is written to a history file at once, and Undo puts the names back. Undo works in the free edition too. An item that was changed after your rename is left alone. Renaming can break links from other files and shortcuts.

Does it find every problem?

It does not claim that. The free edition's list stops at 50 rows, while the counts cover everything. On a made-up folder (paths of 259, 260 and 261 characters, reserved names, names ending with a period or a space) every item that failed in a cmd copy was in the list. Network drives and permission problems were not tested. Folders it cannot read are counted and named, and the check goes on.

Sources

＊1 Microsoft Learn: Maximum Path Length Limitation: https://learn.microsoft.com/en-us/windows/win32/fileio/maximum-file-path-limitation
＊2 Microsoft Learn: robocopy: https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/robocopy

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Questions: the support page or support@hullspark.com. Privacy policy