Chapter 16 · 16.1
Cleaning up files with forbidden characters so Windows syncs again
The question: the desktop app on Windows reports that a number of files cannot be synced, with something like an invalid name or characters that aren't allowed. On the Mac or in the browser, they're just there.
Why: your WebOké Nextcloud allows almost all characters in names, Windows doesn't. Files that were given a name with such a character on a Mac, phone or in the browser can't be saved by Windows. The app then skips them; the rest syncs as normal.
| What Windows doesn't allow | Example | Better |
|---|---|---|
| The characters \ / : * ? " < > | | Minutes 24:10:2026.docx | Minutes 24-10-2026.docx |
| A space or full stop at the end of the name | Quote .docx or folder "Customers " | Quote.docx, folder "Customers" |
| Reserved names | CON, PRN, AUX, NUL, COM1, LPT1 (also with an extension, such as con.txt) | A different name |
| Very long paths | Many folders within folders with long names | Shorter names or fewer levels |

How to fix it
- Click the cloud icon and note down which files the app is skipping. The notification names the file and the folder.
- Open your Nextcloud in the browser and go to that folder.
- Click the three dots next to the file and choose Rename. Give it a name without the characters from the table and press Enter.
- Repeat this for the other files. You rename a folder with such a name in the same way; everything in the folder comes along with it.
- Click the cloud icon: the app will automatically pick up the renamed files on the next round.

Lots of files at once?
- In the browser, type the character, for example a colon or question mark, into the Search here search field at the top left of Files. This helps you find them quickly.
- If they keep coming back, check where they're coming from. It's often a program on a Mac or phone that puts the date with colons in the name, such as a scanning app or a screen recording program. Set up a different naming format there.
- Working with people on Mac and Windows in the same folders? Agree on a rule: no punctuation marks except the hyphen and the underscore.
Please note: rename such files in the browser or on the Mac, not on the Windows computer itself. After all, they don't appear there on Windows.
You can read more about file names that cause problems in File names that cause problems.
