Allowed Names (Entries in File Systems)

List of problematic characters, based on list in a Dropbox page1):

Character Dropbox
macOS
Finder
MS Windows
/ (forward slash) Not Rec.1) Ok No2) \
\ (backslash) Not Rec.1) Ok No2) /
< (less than) Not Rec.1) Ok No2) <
> (greater than) Not Rec.1) Ok No2) >
: (colon) Not Rec.1) No No2) :
” (double quote) Not Rec.1) Ok No2)
| (vertical bar or pipe) Not Rec.1) Ok No2) |
? (question mark) Not Rec.1) Ok No2) ?
* (asterisk) Not Rec.1) Ok No2) *
. (period) Not Rec.1) Ok Ok
emojis or emoticons Not Rec.1) Ok ?
~ (tilde) not ment.1) Ok No2) ~
# (hash) not ment.1) Ok No2) #
% (percent) not ment.1) Ok No2) %
& (ampersand) not ment.1) Ok No2) &
+ (plus) not ment.1) Ok No2) +
– (minus) not ment.1) Ok No2)
{ (opening brace) not ment.1) Ok No2) {
} (closing brace) not ment.1) Ok No2) }

 

Extended list/table, organized on ASCII values

ASCII
(Dec)
Character Dropbox
macOS
Finder
MS Windows
33 ! (excl. mark) Ok Ok
34 ” (double quote) Not Rec.1) Ok No2)
35 # (number, hash) Ok No2)
36 $ (Dollar) Ok Ok
 37 % (per cent) Ok No2)
38 & (ampersand) Ok No2)
39 ‘ (single quote) Ok Ok
40 ( (open parenthesis) Ok Ok
41 ) (closing parenthesis)    
42 * (asterisk) Not Rec.1) Ok No2)
43 + (plus) Ok No2)
44 , (comma)    
45 – (hyphen, minus) Ok No2)
46 . (period, dot, full stop) Not Rec.1) Ok Ok
47 / (slash, divide, forward slash) Not Rec.1) Ok No2)
48..57 numbers 0,1…9 OK OK OK
58 : (colon) Not Rec.1) No No2)
59 ; (semicolon)      
60 < (less than) Not Rec.1) Ok No2)
61 = (equal sign)      
62 > (greater than) Not Rec.1) Ok No2)
63 ? (question mark) Not Rec.1) Ok No2)
64 @ (at symbol)      
65..90 chars, A, B…Z OK OK OK
91 [ (opening bracket)      
92 \ (backslash) Not Rec.1) Ok No2)
93 [ (closing bracket)      
94 ^ (caret, circumflex)      
95 _ (underscore)      
96 ` (grave accent)      
97..122 lower case, a,b…z OK OK OK
123 { (opening brace) Ok No2)
124 | (vertical bar, pipe) Not Rec.1) Ok No2)
125 } (closing brace) Ok No2)
126 ~ (tilde, equivalency sign ) Ok No2)
   
 (Not ASCII) emojis or emoticons Not Rec.1) Ok ?

 

1) Naming Dropbox files and folders – help.dropbox.com/files-folders/sort-preview/file-names
2) Avoid Illegal Characters in File Names! – d2lhelp.view.usg.edu/s/article/KB0016214


Fortunately, most Microsoft Windows computers do not even allow filenames containing any of these “illegal characters” (shown below) to be created or saved in the first place:

\ / : * ? ” < > | ~ # % & + { } –