Why aren't certain files on one computer syncing to another?

To make sure that your files are syncing correctly, first verify that your computers are connected to the Internet and are linked to the same Dropbox account. If you verified that your computers are online and in sync, but a file still isn't appearing where expected, then there may be an issue with the file itself.

Operating systems don't always play nicely with one another. The Dropbox desktop app tracks these inconsistencies and will try its best to resolve the problem gracefully. When it can't, the file will still sync to dropbox.com, but it may not appear or work properly on incompatible operating systems.

To see which of your files may cause syncing problems, sign in to dropbox.com and use the Dropbox bad files check tool.

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To ensure your files and folders sync correctly on other operating systems, try to follow these guidelines:

Incompatible characters for all operating systems

Don't name your files with the following characters, as Dropbox will not sync them on any platform:

  • / (forward slash)
  • \ (backslash)

Note: Dropbox will sync files that include a forward slash in the file name to dropbox.com on Mac computers only. However, these files will sync to dropbox.com with a : (colon) in place of the / (forward slash). Files with forward slashes sync to other Mac computers, but they can't be synced to Windows computers.

Incompatible characters with Windows

When naming your files, avoid characters incompatible with the Windows file system:

  • < (less than)
  • > (greater than)
  • : (colon)
  • " (double quote)
  • | (vertical bar or pipe)
  • ? (question mark)
  • * (asterisk)
  • . (period) or a space at the end of a file or folder name

Reserved filenames in Windows

Windows has a set of reserved words that can’t be used as valid filenames. If you create and name a file or folder from dropbox.com or a non-Windows device that incldues a reserved word, then the file will not sync to your Dropbox on Windows computers. For a complete list of reserved file names, please see the Naming Conventions section of Windows Developer Network.

Ignored files

Some small system files aren't synced over Dropbox. These include:

  • desktop.ini
  • thumbs.db
  • .ds_store
  • icon\r
  • .dropbox
  • .dropbox.attr

Max character length

Windows only allows file and folder names of 260 characters or less; however, current versions of the Dropbox desktop app are able to read and write to locations that are longer than 260 characters long without problems. 

Some applications might still be subject to the operating system limits and may have problems accessing files that are in long paths. Additionally, some applications—such as Microsoft Excel—have shorter limits (218 characters).

For example, if you have an Excel 2010 file in a path that is 261 characters long, Dropbox will sync it to your computer. However, when you try to open it Excel, Dropbox will show an error message like File Cannot be accessed. To fix this problem, shorten the name or move the file or folder to a higher-level folder.

Note: Windows counts the file path as part of the name. This sample file path is 142 characters, not the 16 characters of the file name:

C:\Users\Panda\My Documents\Dropbox\Creative Nonfiction\My Autobiography\Favorite Things\Favorite Foods\Bamboo\Family Recipes\Fresh Leaves.doc

Case conflicts

Most Linux installations allow you to have two files or folders with the same name but different capitalization. However, by default, Mac and Windows won't differentiate file or folder names by case. Therefore, if Dropbox comes across Linux directories named "Sample folder" and "sample folder" (lowercase "s"), it will still sync both folders to Mac and Windows computers. But one folder will appear as a copy of the original folder and will be appended with case conflict.

Beginning characters on Mac and Linux

Files or folders that begin with a period (e.g. .myfile.doc) will sync properly to the Dropbox folder on your computer. However, Mac and Linux operating systems will regard filenames that begin with a period as system files and hide the files automatically. You won’t be able to see the files without modifying advanced settings on your computer. Instead, you can sign in to dropbox.com and rename the files or folders (e.g. _myfolder).

Trailing characters

Files and folders that end with periods (.) won't sync properly between operating systems. If a file ends in a period, like file.txt., the file won't sync and it will appear in bad files check.

Trailing spaces in file and folder names are stripped in order to sync properly with other operating systems. If Dropbox finds a file in your Dropbox folder with the same name but different only in white space (or the character created by pressing the space bar), it will add the file to your Dropbox folder and append the file name with white space conflict.

Temporary files

When some applications (such as Microsoft Word, Excel, or PowerPoint) open a file, they will often save a temporary file in the same directory and name it in one of the following ways:

  • Name begins with ~$ (a tilde and dollar sign) or .~ (a period and tilde)
  • Name begins with a tilde and ends in .tmp, such as ~myfile.tmp

Dropbox does not sync these temporary files on any operating system.

Unicode encoding conflicts

In some instances, there are several ways to create the same character on your keyboard. Although the characters may look the same, they are not the same to operating systems and Dropbox. When Dropbox notices these encoding conflicts, it will create a conflicted copy of the file and save it in the same folder appended with Unicode Encoding Conflict.

Metadata and resource forks

Avoid syncing files that use metadata (or resource forks), including Mac aliases or Windows shortcuts. These types of files typically only work on the operating systems they were created on.

Junction points and aliases

Dropbox will follow Windows junction points (Windows Vista or later) and sync the files or folders they link to. However, any changes to those files or folders made from the Windows operating system will not sync again until the Dropbox desktop app is restarted. To get around this, move the original folder to your Dropbox and add a junction point from its previous location to link to its new location in the Dropbox folder.

A warning regarding metadata and FAT32 drives

Some documents have file attributes, or xattrs, in data attached to the file. We call this data metadata. Operating systems use metadata in many different ways: storing the icon, labeling your documents, attaching information to the file, permissions, and so on. Dropbox supports xattrs on all platforms. However, thumb drives and portable drives that use the FAT32 file system do not support metadata. If your Dropbox folder is on a FAT32 drive, unfortunately it is impossible to retain metadata when the file is moved or renamed.

Monitoring more than 10,000 folders on Linux

The Linux version of the Dropbox desktop app is limited from monitoring more than 10000 folders by default. Anything more than that is not watched and, therefore, ignored when syncing. There's an easy fix for this. Open a terminal and enter the following:

echo fs.inotify.max_user_watches=100000 | sudo tee -a /etc/sysctl.conf; sudo sysctl -p

This command will tell your system to watch up to 100,000 folders. Once the command is entered and you enter your password, Dropbox will immediately resume syncing.

Turning on extended attribute (xattr) support in Linux

Some Linux distributions have extended attributes (xattrs) turned off by default. If you're running a Linux distribution with an ext3 or ext4 file system, it's possible to turn on xattr support, typically through your /etc/fstab settings file. Please refer to your Linux distribution's documentation for instructions.

Using referenced files in Dropbox

We strongly recommend against methods that add referenced files (symlinks, junction points, or networked folders) to the Dropbox folder. Using reference files can cause high CPU usage, poor syncing performance, permissions issues, and quota usage disparities.

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