Why OneDrive keeps renaming your files

OneDrive reserves the ability to alter invalid filenames, regardless of their acceptability elsewhere. OneDrive performs such changes to prevent internal errors and maintain a satisfactory user experience for you. In most cases, an automated file-rename is intentional, albeit avoidable.

OneDrive will keep renaming your files when the filenames contain characters OneDrive deems invalid. Examples of characters that OneDrive deems invalid are: *, :, <, >, and ?, amongst others.

Often using invalid filenames with OneDrive will result in its frequent renaming of your files. I’ll be helping you resolve this problem with a brief guide on invalid filenames.


Can filenames make OneDrive alter my file’s name?

Does my initial filename have an impact

Yes: OneDrive may rename files if it finds its name unacceptable — this is done to avoid confusing your device’s operating system. Thus, if you would like to avoid encountering this issue, I recommend conforming to OneDrive’s filename rules. To do so, you need only avoid a few characters and phrases — which frankly aren’t that common. These characters can be problematic due to their meaning within the OneDrive file directory.

/        Indicates pathing to a new folder
\        Indicates pathing to a new folder
*        Indicates requests for a wildcard/random result
:        Indicates end of a drive name
<        Unknown at this time
>        Unknown at this time
?        Used for advanced file searching
|        Unknown at this time

Character usage

Your character usage plays a large part in OneDrive accepting your filename, and this is because OneDrive disallows a handful of characters you might have considered using. Unsurprisingly these are all “special” characters- though, that’s not to say you can’t have any. For your convenience, I’ve left a list of recently tested characters found not to work with OneDrive. For those unfamiliar, “special” characters refer are the various non-alphanumeric characters made available to you.

"        *        :        <        >        ?        /        \        |

Under normal circumstances, you cannot create files containing the above characters due to their use in most operating systems. Take, for instance, “*” which indicates a wildcard, “/” and “\” which we use for navigating our file directories.

Attempting to use special characters

Overall filename

In addition to preventing the usage of particular characters, OneDrive also considers specific names to be invalid. This error is not a fault of OneDrive directly but an issue present in even the oldest Windows installations. Before today’s modern computer systems, external devices like your office printer and input ports were interacted with via an associated document on the system. As such, if you just finished composing a letter and wished to print it, you would save it to the PRN document- where your printer would read and print the file.

CON    PRN    AUX    NUL    COM0 (COM0 through COM9)    LPT0 (LPT0 through LPT9)    desktop.ini

Above are the reserved filenames you should avoid using with OneDrive. Despite having little to no need for this dated system, Microsoft continues to reserve such filenames so that Windows (and OneDrive) may remain backward compatible with older systems.

Contained strings

The final contributing factor to a filename’s validity is whether or not it contains one of two disallowed strings. If any filename begins with ~$ it will immediately be deemed invalid. Similarly, any filename containing _vti_ will also be considered invalid. Despite not being specifically ~$ or _vti_ the examples shown below would both be considered invalid filenames.


Bypassing disallowed filenames in OneDrive

If for whatever reason, you’re adamant about using one of the disallowed filenames, you may take comfort in knowing they can easily be made valid with a minor addition. The addition is an underscore prefixing the filename or suffixing it- before the file extension.

Prefixed variants

_CON  _PRN  _AUX  _NUL  _COM0 (COM0 through COM9)  _LPT0 (LPT0 through LPT9)  _desktop.ini

Suffixed variants

CON_  PRN_  AUX_  NUL_  COM0_ (COM0 through COM9)  LPT0_ (LPT0 through LPT9)  desktop.ini_

Are sync conflicts making my OneDrive filenames change?

What is a sync conflict?

A sync conflict is a problematic occurrence found in OneDrive when OneDrive cannot merge multiple variants of a file. For example, if you have a file stored on OneDrive containing the word “music,” you have no issue. However, let’s say your laptop (which isn’t yet syncing) contains the same file, but you change the word to “piano.” Normally when you start syncing your laptop with OneDrive, it would detect the “piano” version to be the most recent and update itself accordingly. However, in this example, you’ve also changed the file on your PC, to contain “guitar.” Now, when both devices are attempting to sync, OneDrive perceives two “most recent versions” and cannot determine which to merge.

How are sync conflicts handled by OneDrive?

When a sync conflict occurs, OneDrive prioritizes the safety of your documents and avoids completely overwriting one version in favor of the other. Instead, OneDrive will create a separate file with your device’s name appended to the original filename where one version will be stored, and place the other version’s changes in the original file.

The answer

No. While OneDrive alters filenames in this instance, it alters the name of a copy of your file. Because of this, it would be unfair to state sync conflicts are a notable cause for filename changes.

Recap & Farewell


When you give a file an invalid filename, you invite OneDrive to disallow your file or rename it. Invalid filenames can be invalid for several reasons: unaccepted “special” characters, usage of a reserved filename, or usage of an unaccepted string within your filename. While you can use some reserved filenames with a single character addition, certain restricted strings are in no way bypassable. Contrary to what some may think, OneDrive sync conflicts are not related to filename changes, actually being the cause of unintended file duplicates.


Greetings reader, I hope this post was of use to you, or at the very least shed some light on what could be going wrong. Here at Business Tech Planet, we’re constantly working hard to produce comprehensive and viable resources detailing the solutions to various Microsoft365 issues, exploring their new additions and features, and answering common queries.

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Jack Mitchell

Jack Mitchell has been the Operations manager at telecoms and MSP Optionbox for more than 4 years. He has played a crucial role in the company, from marketing to helpdesk, and ensures that the IT requirements of over 300 clients are continuously met. With his innate passion for technology and troubleshooting and a particular interest in Apple products, Jack now delivers the most comprehensive tech guides to make your life easier. You can connect with Jack on LinkedIn.

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