Allowable characters and filenames on Proton Drive

When you upload a file onto Proton Drive, you can keep the filename it previously had or you can rename it to help you stay organized.

In either case, there are some limits that Proton Drive imposes and other limits or restricted characters that your operating system (OS) might impose. 

This article explains what constraints your filenames must meet and how your filenames might change if you download them back onto your device. 

Filenames in Proton Drive

When you’re naming your file on Proton Drive, you can use any text, and Proton Drive supports all Unicode characters. The two main requirements are:

• All filenames must be between 1 and 255 characters
• No two files, two folders, or file and folder can have the same name in the same location. (For example, you cannot have a file and folder both named 2023 taxes appear next to each other on a screen. However, you can have multiple files and folders named 2023 taxes as long as they are contained in different folders or locations.)

The Proton Drive web app places no restriction on characters on node names. It supports all Unicode characters.

However, the Proton Drive web application does apply the following restrictions to node names:

Restriction	Example	Notes
period (“.”) or two periods (“..”)	“.””..”
space (” “) at the beginning	” filename.txt”
space (” “) at the end	“filename.txt “
period (“.”) at the end	“filename.”
Right to left override	‮”filename.txt”	https://unicode.flopp.net/c/202E(new window)
Narrow no-break space	“ filename.txt”	https://unicode.flopp.net/c/202F(new window)
Invisible characters	” ‎invisible_chars.txt”
Other space and invisible characters		https://unicode.flopp.net/c/2000(new window) https://unicode.flopp.net/c/2001(new window) https://unicode.flopp.net/c/2002(new window) https://unicode.flopp.net/c/2003(new window) https://unicode.flopp.net/c/2004(new window) https://unicode.flopp.net/c/2005(new window) https://unicode.flopp.net/c/2006(new window) https://unicode.flopp.net/c/2007(new window) https://unicode.flopp.net/c/2008(new window) https://unicode.flopp.net/c/2009(new window) https://unicode.flopp.net/c/200A(new window) https://unicode.flopp.net/c/200B(new window) https://unicode.flopp.net/c/200C(new window) https://unicode.flopp.net/c/200D(new window)

Operating system limitations on filenames

While Proton Drive does not place limits on the characters you can use for filenames, many operating systems do. 

Often your device’s operating system will resolve any unsupported characters or filenames itself by suggesting new characters or filenames that it does support.

Similarly, Proton Drive recognizes the differences between uppercase and lowercase letters in filenames. For example, the following filenames would be acceptable on Proton Drive for three different files:

•  filename
•  Filename
•  fileName

However, if you downloaded these files onto a device using a different OS, it might rename them. For example, if you downloaded the three previously mentioned files on Windows, it would add numbering to the names:

• Filename (1)
• Filename (2)
• Filename (3)

Unsupported characters by operating system

Character	Description	OS / Filesystem	Notes
0x00		Windows, Linux
0x01 – 0x1F		Windows
<	less than	Windows
>	greater than	Windows
:	colon	Windows
“	double quote	Windows
/	forward slash	Windows, Mac OS X, Linux
\	backslash	Windows
|	vertical bar or pipe	Windows
?	question mark	Windows
*	asterisk	Windows

Unsupported names by operating system

File / folder name	Example	OS / Filesystem	Notes
period (“.”) or two periods (“..”)	“.””..”	Windows, Mac OS X, Linux	Windows API removes ending spaces and periods before processing.
“CON”, “PRN”, “AUX”, “NUL”,”COM1″, “COM2”, “COM3”, “COM4”, “COM5”, “COM6”, “COM7”, “COM8”, “COM9″,”LPT1”, “LPT2”, “LPT3”, “LPT4”, “LPT5”, “LPT6”, “LPT7”, “LPT8”, “LPT9”		Windows	DOS device names
space (” “) at the beginning	” filename.txt”	Windows
space (” “) at the end	“filename.txt “	Windows	Windows API removes ending spaces and periods before processing.
period (“.”) at the end	“filename.”	Windows	Windows API removes ending spaces and periods before processing.

For more Windows file naming conventions see: https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file(new window)