Recently I have made the decision to switch from Google to Microsoft for my personal (e-mail) account and related services. This means I had to move over a lot of data from Google’s servers to Microsoft, including my e-mail inbox, documents and pictures. When using the OneDrive synchronisation client on my Mac (a piece of software as part of the Microsoft 365 suite), I came across an issue. OneDrive was complaining with the clear message: OneDrive needs your attention. Given that I was synchronising my personal files – which are important to me – I was certainly curious what OneDrive is warning me for.

The name contains characters that aren’t allowed

In my case, I received a red error banner in the synchronisation window while my files were uploading to the cloud. clicked on that message, and the OneDrive client would tell me which files were affected. Somehow, these files / folders contained some invalid characters, or something else was preventing these files and folders from being uploaded to the cloud.

Upon checking the files, I could not immediately find what was the issue. There were 2 file names: Car Insurance and Travels 2019. No special characters at all as you can see. I checked the Microsoft documentation and sure enough, there are some forbidden characters:

”     *     :     <    >    ?    /    \    |

These characters have a special meaning on the Windows operating system, so they can’t be used to prevent all kinds of possible issues. And additionally, there are some reserved words as well:

AUX, PRN, NUL, CON, COM0, COM1, COM2, COM3, COM4, COM5, COM6, COM7, COM8, COM9, LPT0, LPT1, LPT2, LPT3, LPT4, LPT5, LPT6, LPT7, LPT8, LPT9.

But as you can see, none of these special characters or special words have been used in my case! So I tried some other tricks: restarting the OneDrive client on my computer, restarting the computer itself, reconnecting to my Wi-Fi at home, …

In the end, I discovered there is a space in the folder name. While it was not immediately clear from the description on Microsoft’s support website, but this is apparently also an issue for OneDrive. I removed the space (which was situated at the end of the folder) and the issue was no longer there.

Hope this helps you as well!