How to encode the filename parameter of Content-Disposition header in HTTP

Question

Web applications that want to force a resource to be downloaded rather than directly rendered in a Web browser issue a Content-Disposition header in the HTTP response of the form   Content-Disposition  attachment  filename FILENAME  The filename parameter can be used to suggest a name for the file into which the resource is downloaded by the browser  RFC 2183  Content-Disposition   however  states in section 2 3  The Filename Parameter  that the file name can only use US-ASCII characters      Current  RFC 2045  grammar restricts   parameter values  and hence   Content-Disposition filenames  to   US-ASCII   We recognize the great   desirability of allowing arbitrary   character sets in filenames  but it is   beyond the scope of this document to   define the necessary mechanisms    There is empirical evidence  nevertheless  that most popular Web browsers today seem to permit non-US-ASCII characters yet  for the lack of a standard  disagree on the encoding scheme and character set specification of the file name  Question is then  what are the various schemes and encodings employed by the popular browsers if the file name    na  vefile     without quotes and where the third letter is U 00EF  needed to be encoded into the Content-Disposition header   For the purpose of this question  popular browsers being    Firefox  Internet Explorer  Safari Google Chrome  Opera

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RFC 6266 describes the    Use of the Content-Disposition Header Field in the Hypertext Transfer Protocol  HTTP      Quoting from that      6  Internationalization Considerations      The    filename     parameter  Section 4 3   using the encoding defined   in  RFC5987   allows the server to transmit characters outside the   ISO-8859-1 character set  and also to optionally specify the language   in use    And in their examples section      This example is the same as the one above  but adding the  filename    parameter for compatibility with user agents not implementing   RFC 5987   Content-Disposition  attachment                       filename  EURO rates                        filename  utf-8   e2 82 ac 20rates       Note  Those user agents that do not support the RFC 5987 encoding   ignore    filename     when it occurs after    filename       In Appendix D there is also a long list of suggestions to increase interoperability  It also points at a site which compares implementations  Current all-pass tests suitable for common file names include    attwithisofnplain  plain ISO-8859-1 file name with double quotes and without encoding  This requires a file name which is all ISO-8859-1 and does not contain percent signs  at least not in front of hex digits  attfnboth  two parameters in the order described above  Should work for most file names on most browsers  although IE8 will use the    filename    parameter    That RFC 5987 in turn references RFC 2231  which describes the actual format  2231 is primarily for mail  and 5987 tells us what parts may be used for HTTP headers as well  Don t confuse this with MIME headers used inside a multipart form-data HTTP body  which is governed by RFC 2388  section 4 4 in particular  and the HTML 5 draft

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If you are using a nodejs backend you can use the following code I found here  var fileName    my file 2  txt   var header    Content-Disposition  attachment  filename  UTF-8                    encodeRFC5987ValueChars fileName    function encodeRFC5987ValueChars  str        return encodeURIComponent str              Note that although RFC3986 reserves      RFC5987 does not             so we do not need to escape it         replace        g  escape      i e    27  28  29         replace     g    2A                   The following are not required for percent-encoding per RFC5987                  so we can allow for a little better readability over the wire                  replace      7C 60 5E  g  unescape

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I normally URL-encode  with  xx  the filenames  and it seems to work in all browsers  You might want to do some tests anyway

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The following document linked from the draft RFC mentioned by Jim in his answer further addresses the question and definitely worth a direct note here   Test Cases for HTTP Content-Disposition header and RFC 2231 2047 Encoding

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Put the file name in double quotes  Solved the problem for me  Like this   Content-Disposition  attachment  filename  My Report doc    http   kb mozillazine org Filenames with spaces are truncated upon download  I ve tested multiple options  Browsers do not support the specs and act differently  I believe double quotes is the best option

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Just an update since I was trying all this stuff today in response to a customer issue   With the exception of Safari configured for Japanese  all browsers our customer tested worked best with filename text pdf - where text is a customer value serialized by ASP Net IIS in utf-8 without url encoding   For some reason  Safari configured for English would accept and properly save a file with utf-8 Japanese name but that same browser configured for Japanese would save the file with the utf-8 chars uninterpreted   All other browsers tested seemed to work best fine  regardless of language configuration  with the filename utf-8 encoded without url encoding  I could not find a single browser implementing Rfc5987 8187 at all   I tested with the latest Chrome  Firefox builds plus IE 11 and Edge   I tried setting the header with just filename  utf-8  texturlencoded pdf  setting it with both filename text pdf  filename  utf-8  texturlencoded pdf   Not one feature of Rfc5987 8187 appeared to be getting processed correctly in any of the above

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The following document linked from the draft RFC mentioned by Jim in his answer further addresses the question and definitely worth a direct note here   Test Cases for HTTP Content-Disposition header and RFC 2231 2047 Encoding

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We had a similar problem in a web application  and ended up by reading the filename from the HTML  lt input type  file  gt   and setting that in the url-encoded form  in a new HTML  lt input type  hidden  gt   Of course we had to remove the path like  C  fakepath   that is returned by some browsers    Of course this does not directly answer OPs question  but may be a solution for others

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PHP framework Symfony 4 has  filenameFallback in HeaderUtils  makeDisposition  You can look into this function for details - it is similar to the answers above   Usage example    filenameFallback   preg replace            md5  filename          filename    disposition    response- gt headers- gt makeDisposition ResponseHeaderBag  DISPOSITION ATTACHMENT   filename   filenameFallback    response- gt headers- gt set  Content-Disposition    disposition

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I normally URL-encode  with  xx  the filenames  and it seems to work in all browsers  You might want to do some tests anyway

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In PHP this did it for me  assuming the filename is UTF8 encoded    header  Content-Disposition  attachment          filename      addslashes utf8 decode  filename                 filename  utf-8        rawurlencode  filename      Tested against IE8-11  Firefox and Chrome  If the browser can interpret filename  utf-8 it will use the UTF8 version of the filename  else it will use the decoded filename  If your filename contains characters that can t be represented in ISO-8859-1 you might want to consider using iconv instead

User · Answer

The following document linked from the draft RFC mentioned by Jim in his answer further addresses the question and definitely worth a direct note here   Test Cases for HTTP Content-Disposition header and RFC 2231 2047 Encoding

User · Answer

in asp net mvc2 i use something like this   return File      tempFile        application octet-stream        HttpUtility UrlPathEncode fileName           I guess if you don t use mvc 2  you could just encode the filename using  HttpUtility UrlPathEncode fileName

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I know this is an old post but it is still very relevant  I have found that modern browsers support rfc5987  which allows utf-8 encoding  percentage encoded  url-encoded   Then Na  ve file txt becomes   Content-Disposition  attachment  filename  UTF-8  Na C3 AFve 20file txt   Safari  5  does not support this  Instead you should use the Safari standard of writing the file name directly in your utf-8 encoded header   Content-Disposition  attachment  filename Na  ve file txt   IE8 and older don t support it either and you need to use the IE standard of utf-8 encoding  percentage encoded   Content-Disposition  attachment  filename Na C3 AFve 20file txt   In ASP Net I use the following code   string contentDisposition  if  Request Browser Browser     IE   amp  amp   Request Browser Version     7 0     Request Browser Version     8 0        contentDisposition    attachment  filename     Uri EscapeDataString fileName   else if  Request Browser Browser     Safari       contentDisposition    attachment  filename     fileName  else     contentDisposition    attachment  filename  UTF-8      Uri EscapeDataString fileName   Response AddHeader  Content-Disposition   contentDisposition     I tested the above using IE7  IE8  IE9  Chrome 13  Opera 11  FF5  Safari 5   Update November 2013   Here is the code I currently use  I still have to support IE8  so I cannot get rid of the first part  It turns out that browsers on Android use the built in Android download manager and it cannot reliably parse file names in the standard way   string contentDisposition  if  Request Browser Browser     IE   amp  amp   Request Browser Version     7 0     Request Browser Version     8 0        contentDisposition    attachment  filename     Uri EscapeDataString fileName   else if  Request UserAgent    null  amp  amp  Request UserAgent ToLowerInvariant   Contains  android       android built-in download manager  all browsers on android      contentDisposition    attachment  filename       MakeAndroidSafeFileName fileName          else     contentDisposition    attachment  filename       fileName        filename  UTF-8      Uri EscapeDataString fileName   Response AddHeader  Content-Disposition   contentDisposition     The above now tested in IE7-11  Chrome 32  Opera 12  FF25  Safari 6  using this filename for download    abcABC                                                    amp                        -    txt  On IE7 it works for some characters but not all  But who cares about IE7 nowadays   This is the function I use to generate safe file names for Android  Note that I don t know which characters are supported on Android but that I have tested that these work for sure   private static readonly Dictionary lt char  char gt  AndroidAllowedChars    abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ  -                       0123456789  ToDictionary c   gt  c   private string MakeAndroidSafeFileName string fileName        char   newFileName   fileName ToCharArray        for  int i   0  i  lt  newFileName Length  i                  if   AndroidAllowedChars ContainsKey newFileName i                newFileName i                   return new string newFileName        TomZ  I tested in IE7 and IE8 and it turned out that I did not need to escape apostrophe      Do you have an example where it fails    Dave Van den Eynde  Combining the two file names on one line as according to RFC6266 works except for Android and IE7 8 and I have updated the code to reflect this  Thank you for the suggestion    Thilo  No idea about GoodReader or any other non-browser  You might have some luck using the Android approach    Alex Zhukovskiy  I don t know why but as discussed on Connect it doesn t seem to work terribly well

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In PHP this did it for me  assuming the filename is UTF8 encoded    header  Content-Disposition  attachment          filename      addslashes utf8 decode  filename                 filename  utf-8        rawurlencode  filename      Tested against IE8-11  Firefox and Chrome  If the browser can interpret filename  utf-8 it will use the UTF8 version of the filename  else it will use the decoded filename  If your filename contains characters that can t be represented in ISO-8859-1 you might want to consider using iconv instead

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In ASP NET Web API  I url encode the filename   public static class HttpRequestMessageExtensions       public static HttpResponseMessage CreateFileResponse this HttpRequestMessage request  byte   data  string filename  string mediaType                HttpResponseMessage response   new HttpResponseMessage HttpStatusCode OK           var stream   new MemoryStream data           stream Position   0           response Content   new StreamContent stream            response Content Headers ContentType                new MediaTypeHeaderValue mediaType               URL-Encode filename            Fixes behavior in IE  that filenames with non US-ASCII characters            stay correct  not   utf-8                       var encodedFilename   HttpUtility UrlEncode filename  Encoding UTF8            response Content Headers ContentDisposition               new ContentDispositionHeaderValue  attachment     FileName   encodedFilename            return response

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I normally URL-encode  with  xx  the filenames  and it seems to work in all browsers  You might want to do some tests anyway

User · Answer

There is discussion of this  including links to browser testing and backwards compatibility  in the proposed RFC 5987   Character Set and Language Encoding for Hypertext Transfer Protocol  HTTP  Header Field Parameters    RFC 2183 indicates that such headers should be encoded according to RFC 2184  which was obsoleted by RFC 2231  covered by the draft RFC above

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I use the following code snippets for encoding  assuming fileName contains the filename and extension of the file  i e   test txt      PHP   if   strpos     SERVER    HTTP USER AGENT      MSIE     gt  0          header    Content-Disposition  attachment  filename      rawurlencode    fileName              else        header   Content-Disposition  attachment  filename  UTF-8        rawurlencode    fileName          Java   fileName   request getHeader    user-agent    contains    MSIE      URLEncoder encode   fileName   utf-8     MimeUtility encodeWord   fileName    response setHeader    Content-disposition    attachment  filename       fileName

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If you are using a nodejs backend you can use the following code I found here  var fileName    my file 2  txt   var header    Content-Disposition  attachment  filename  UTF-8                    encodeRFC5987ValueChars fileName    function encodeRFC5987ValueChars  str        return encodeURIComponent str              Note that although RFC3986 reserves      RFC5987 does not             so we do not need to escape it         replace        g  escape      i e    27  28  29         replace     g    2A                   The following are not required for percent-encoding per RFC5987                  so we can allow for a little better readability over the wire                  replace      7C 60 5E  g  unescape

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I ended up with the following code in my  download php  script  based on this blogpost and these test cases     il1 filename   utf8 decode  filename    to underscore              lt  gt       safe filename   strtr  il1 filename   to underscore  str repeat      strlen  to underscore      header  Content-Disposition  attachment  filename    safe filename        safe filename      filename           filename  UTF-8    rawurlencode  filename        This uses the standard way of filename       as long as there are only iso-latin1 and  safe  characters used  if not  it adds the filename  UTF-8   url-encoded way  According to this specific test case  it should work from MSIE9 up  and on recent FF  Chrome  Safari  on lower MSIE version  it should offer filename containing the ISO8859-1 version of the filename  with underscores on characters not in this encoding   Final note  the max  size for each header field is 8190 bytes on apache  UTF-8 can be up to four bytes per character  after rawurlencode  it is x3   12 bytes per one character  Pretty inefficient  but it should still be theoretically possible to have more than 600  smiles   F0 9F 98 81 in the filename

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Just an update since I was trying all this stuff today in response to a customer issue   With the exception of Safari configured for Japanese  all browsers our customer tested worked best with filename text pdf - where text is a customer value serialized by ASP Net IIS in utf-8 without url encoding   For some reason  Safari configured for English would accept and properly save a file with utf-8 Japanese name but that same browser configured for Japanese would save the file with the utf-8 chars uninterpreted   All other browsers tested seemed to work best fine  regardless of language configuration  with the filename utf-8 encoded without url encoding  I could not find a single browser implementing Rfc5987 8187 at all   I tested with the latest Chrome  Firefox builds plus IE 11 and Edge   I tried setting the header with just filename  utf-8  texturlencoded pdf  setting it with both filename text pdf  filename  utf-8  texturlencoded pdf   Not one feature of Rfc5987 8187 appeared to be getting processed correctly in any of the above

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I tested the following code in all major browsers  including older Explorers  via the compatibility mode   and it works well everywhere    filename     GET  file      this string from   GET is already decoded if  strstr   SERVER  HTTP USER AGENT    MSIE       filename   rawurlencode  filename   header  Content-Disposition  attachment  filename     filename

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There is no interoperable way to encode non-ASCII names in Content-Disposition  Browser compatibility is a mess  The theoretically correct syntax for use of UTF-8 in Content-Disposition is very weird  filename  UTF-8  foo c3 a4  yes  that s an asterisk  and no quotes except an empty single quote in the middle  This header is kinda-not-quite-standard  HTTP 1 1 spec acknowledges its existence  but doesn t require clients to support it     There is a simple and very robust alternative  use a URL that contains the filename you want   When the name after the last slash is the one you want  you don t need any extra headers   This trick works    real script php fake filename doc   And if your server supports URL rewriting  e g  mod rewrite in Apache  then you can fully hide the script part   Characters in URLs should be in UTF-8  urlencoded byte-by-byte    mot C3 B6rhead     mot  rhead

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PHP framework Symfony 4 has  filenameFallback in HeaderUtils  makeDisposition  You can look into this function for details - it is similar to the answers above   Usage example    filenameFallback   preg replace            md5  filename          filename    disposition    response- gt headers- gt makeDisposition ResponseHeaderBag  DISPOSITION ATTACHMENT   filename   filenameFallback    response- gt headers- gt set  Content-Disposition    disposition

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There is discussion of this  including links to browser testing and backwards compatibility  in the proposed RFC 5987   Character Set and Language Encoding for Hypertext Transfer Protocol  HTTP  Header Field Parameters    RFC 2183 indicates that such headers should be encoded according to RFC 2184  which was obsoleted by RFC 2231  covered by the draft RFC above

User · Answer

There is no interoperable way to encode non-ASCII names in Content-Disposition  Browser compatibility is a mess  The theoretically correct syntax for use of UTF-8 in Content-Disposition is very weird  filename  UTF-8  foo c3 a4  yes  that s an asterisk  and no quotes except an empty single quote in the middle  This header is kinda-not-quite-standard  HTTP 1 1 spec acknowledges its existence  but doesn t require clients to support it     There is a simple and very robust alternative  use a URL that contains the filename you want   When the name after the last slash is the one you want  you don t need any extra headers   This trick works    real script php fake filename doc   And if your server supports URL rewriting  e g  mod rewrite in Apache  then you can fully hide the script part   Characters in URLs should be in UTF-8  urlencoded byte-by-byte    mot C3 B6rhead     mot  rhead

User · Answer

The following document linked from the draft RFC mentioned by Jim in his answer further addresses the question and definitely worth a direct note here   Test Cases for HTTP Content-Disposition header and RFC 2231 2047 Encoding

User · Answer

There is no interoperable way to encode non-ASCII names in Content-Disposition  Browser compatibility is a mess  The theoretically correct syntax for use of UTF-8 in Content-Disposition is very weird  filename  UTF-8  foo c3 a4  yes  that s an asterisk  and no quotes except an empty single quote in the middle  This header is kinda-not-quite-standard  HTTP 1 1 spec acknowledges its existence  but doesn t require clients to support it     There is a simple and very robust alternative  use a URL that contains the filename you want   When the name after the last slash is the one you want  you don t need any extra headers   This trick works    real script php fake filename doc   And if your server supports URL rewriting  e g  mod rewrite in Apache  then you can fully hide the script part   Characters in URLs should be in UTF-8  urlencoded byte-by-byte    mot C3 B6rhead     mot  rhead

User · Answer

There is discussion of this  including links to browser testing and backwards compatibility  in the proposed RFC 5987   Character Set and Language Encoding for Hypertext Transfer Protocol  HTTP  Header Field Parameters    RFC 2183 indicates that such headers should be encoded according to RFC 2184  which was obsoleted by RFC 2231  covered by the draft RFC above

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I tested the following code in all major browsers  including older Explorers  via the compatibility mode   and it works well everywhere    filename     GET  file      this string from   GET is already decoded if  strstr   SERVER  HTTP USER AGENT    MSIE       filename   rawurlencode  filename   header  Content-Disposition  attachment  filename     filename

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Classic ASP Solution Most modern browsers support passing the Filename as UTF-8 now but as was the case with a File Upload solution I use that was based on FreeASPUpload Net  site no longer exists  link points to archive org  it wouldn t work as the parsing of the binary relied on reading single byte ASCII encoded strings  which worked fine when you passed UTF-8 encoded data until you get to characters ASCII doesn t support  However I was able to find a solution to get the code to read and parse the binary as UTF-8  Public Function BytesToString bytes      UTF-8     Dim bslen   Dim i  k   N    Dim b   count    Dim str    bslen   LenB bytes    str  quot  quot     i   0   Do While i  lt  bslen     b   AscB MidB bytes i 1 1        If  b And  amp HFC     amp HFC Then       count   6       N   b And  amp H1     ElseIf  b And  amp HF8     amp HF8 Then       count   5       N   b And  amp H3     ElseIf  b And  amp HF0     amp HF0 Then       count   4       N   b And  amp H7     ElseIf  b And  amp HE0     amp HE0 Then       count   3       N   b And  amp HF     ElseIf  b And  amp HC0     amp HC0 Then       count   2       N   b And  amp H1F     Else       count   1       str   str  amp  Chr b      End If      If i   count - 1  gt  bslen Then       str   str amp  quot   quot        Exit Do     End If      If count gt 1 then       For k   1 To count - 1         b   AscB MidB bytes i k 1 1           N   N    amp H40    b And  amp H3F        Next       str   str  amp  ChrW N      End If     i   i   count   Loop    BytesToString   str End Function  Credit goes to Pure ASP File Upload by implementing the BytesToString   function from include aspuploader asp in my own code I was able to get UTF-8 filenames working   Useful Links  Multipart form-data and UTF-8 in a ASP Classic application  Unicode  UTF  ASCII  ANSI format differences

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in asp net mvc2 i use something like this   return File      tempFile        application octet-stream        HttpUtility UrlPathEncode fileName           I guess if you don t use mvc 2  you could just encode the filename using  HttpUtility UrlPathEncode fileName

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Classic ASP Solution Most modern browsers support passing the Filename as UTF-8 now but as was the case with a File Upload solution I use that was based on FreeASPUpload Net  site no longer exists  link points to archive org  it wouldn t work as the parsing of the binary relied on reading single byte ASCII encoded strings  which worked fine when you passed UTF-8 encoded data until you get to characters ASCII doesn t support  However I was able to find a solution to get the code to read and parse the binary as UTF-8  Public Function BytesToString bytes      UTF-8     Dim bslen   Dim i  k   N    Dim b   count    Dim str    bslen   LenB bytes    str  quot  quot     i   0   Do While i  lt  bslen     b   AscB MidB bytes i 1 1        If  b And  amp HFC     amp HFC Then       count   6       N   b And  amp H1     ElseIf  b And  amp HF8     amp HF8 Then       count   5       N   b And  amp H3     ElseIf  b And  amp HF0     amp HF0 Then       count   4       N   b And  amp H7     ElseIf  b And  amp HE0     amp HE0 Then       count   3       N   b And  amp HF     ElseIf  b And  amp HC0     amp HC0 Then       count   2       N   b And  amp H1F     Else       count   1       str   str  amp  Chr b      End If      If i   count - 1  gt  bslen Then       str   str amp  quot   quot        Exit Do     End If      If count gt 1 then       For k   1 To count - 1         b   AscB MidB bytes i k 1 1           N   N    amp H40    b And  amp H3F        Next       str   str  amp  ChrW N      End If     i   i   count   Loop    BytesToString   str End Function  Credit goes to Pure ASP File Upload by implementing the BytesToString   function from include aspuploader asp in my own code I was able to get UTF-8 filenames working   Useful Links  Multipart form-data and UTF-8 in a ASP Classic application  Unicode  UTF  ASCII  ANSI format differences

User · Answer

Put the file name in double quotes  Solved the problem for me  Like this   Content-Disposition  attachment  filename  My Report doc    http   kb mozillazine org Filenames with spaces are truncated upon download  I ve tested multiple options  Browsers do not support the specs and act differently  I believe double quotes is the best option

User · Answer

There is no interoperable way to encode non-ASCII names in Content-Disposition  Browser compatibility is a mess  The theoretically correct syntax for use of UTF-8 in Content-Disposition is very weird  filename  UTF-8  foo c3 a4  yes  that s an asterisk  and no quotes except an empty single quote in the middle  This header is kinda-not-quite-standard  HTTP 1 1 spec acknowledges its existence  but doesn t require clients to support it     There is a simple and very robust alternative  use a URL that contains the filename you want   When the name after the last slash is the one you want  you don t need any extra headers   This trick works    real script php fake filename doc   And if your server supports URL rewriting  e g  mod rewrite in Apache  then you can fully hide the script part   Characters in URLs should be in UTF-8  urlencoded byte-by-byte    mot C3 B6rhead     mot  rhead

User · Answer

There is discussion of this  including links to browser testing and backwards compatibility  in the proposed RFC 5987   Character Set and Language Encoding for Hypertext Transfer Protocol  HTTP  Header Field Parameters    RFC 2183 indicates that such headers should be encoded according to RFC 2184  which was obsoleted by RFC 2231  covered by the draft RFC above

User · Answer

RFC 6266 describes the    Use of the Content-Disposition Header Field in the Hypertext Transfer Protocol  HTTP      Quoting from that      6  Internationalization Considerations      The    filename     parameter  Section 4 3   using the encoding defined   in  RFC5987   allows the server to transmit characters outside the   ISO-8859-1 character set  and also to optionally specify the language   in use    And in their examples section      This example is the same as the one above  but adding the  filename    parameter for compatibility with user agents not implementing   RFC 5987   Content-Disposition  attachment                       filename  EURO rates                        filename  utf-8   e2 82 ac 20rates       Note  Those user agents that do not support the RFC 5987 encoding   ignore    filename     when it occurs after    filename       In Appendix D there is also a long list of suggestions to increase interoperability  It also points at a site which compares implementations  Current all-pass tests suitable for common file names include    attwithisofnplain  plain ISO-8859-1 file name with double quotes and without encoding  This requires a file name which is all ISO-8859-1 and does not contain percent signs  at least not in front of hex digits  attfnboth  two parameters in the order described above  Should work for most file names on most browsers  although IE8 will use the    filename    parameter    That RFC 5987 in turn references RFC 2231  which describes the actual format  2231 is primarily for mail  and 5987 tells us what parts may be used for HTTP headers as well  Don t confuse this with MIME headers used inside a multipart form-data HTTP body  which is governed by RFC 2388  section 4 4 in particular  and the HTML 5 draft

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I use the following code snippets for encoding  assuming fileName contains the filename and extension of the file  i e   test txt      PHP   if   strpos     SERVER    HTTP USER AGENT      MSIE     gt  0          header    Content-Disposition  attachment  filename      rawurlencode    fileName              else        header   Content-Disposition  attachment  filename  UTF-8        rawurlencode    fileName          Java   fileName   request getHeader    user-agent    contains    MSIE      URLEncoder encode   fileName   utf-8     MimeUtility encodeWord   fileName    response setHeader    Content-disposition    attachment  filename       fileName

User · Answer

I normally URL-encode  with  xx  the filenames  and it seems to work in all browsers  You might want to do some tests anyway

User · Answer

We had a similar problem in a web application  and ended up by reading the filename from the HTML  lt input type  file  gt   and setting that in the url-encoded form  in a new HTML  lt input type  hidden  gt   Of course we had to remove the path like  C  fakepath   that is returned by some browsers    Of course this does not directly answer OPs question  but may be a solution for others

User · Answer

In ASP NET Web API  I url encode the filename   public static class HttpRequestMessageExtensions       public static HttpResponseMessage CreateFileResponse this HttpRequestMessage request  byte   data  string filename  string mediaType                HttpResponseMessage response   new HttpResponseMessage HttpStatusCode OK           var stream   new MemoryStream data           stream Position   0           response Content   new StreamContent stream            response Content Headers ContentType                new MediaTypeHeaderValue mediaType               URL-Encode filename            Fixes behavior in IE  that filenames with non US-ASCII characters            stay correct  not   utf-8                       var encodedFilename   HttpUtility UrlEncode filename  Encoding UTF8            response Content Headers ContentDisposition               new ContentDispositionHeaderValue  attachment     FileName   encodedFilename            return response

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I ended up with the following code in my  download php  script  based on this blogpost and these test cases     il1 filename   utf8 decode  filename    to underscore              lt  gt       safe filename   strtr  il1 filename   to underscore  str repeat      strlen  to underscore      header  Content-Disposition  attachment  filename    safe filename        safe filename      filename           filename  UTF-8    rawurlencode  filename        This uses the standard way of filename       as long as there are only iso-latin1 and  safe  characters used  if not  it adds the filename  UTF-8   url-encoded way  According to this specific test case  it should work from MSIE9 up  and on recent FF  Chrome  Safari  on lower MSIE version  it should offer filename containing the ISO8859-1 version of the filename  with underscores on characters not in this encoding   Final note  the max  size for each header field is 8190 bytes on apache  UTF-8 can be up to four bytes per character  after rawurlencode  it is x3   12 bytes per one character  Pretty inefficient  but it should still be theoretically possible to have more than 600  smiles   F0 9F 98 81 in the filename

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I know this is an old post but it is still very relevant  I have found that modern browsers support rfc5987  which allows utf-8 encoding  percentage encoded  url-encoded   Then Na  ve file txt becomes   Content-Disposition  attachment  filename  UTF-8  Na C3 AFve 20file txt   Safari  5  does not support this  Instead you should use the Safari standard of writing the file name directly in your utf-8 encoded header   Content-Disposition  attachment  filename Na  ve file txt   IE8 and older don t support it either and you need to use the IE standard of utf-8 encoding  percentage encoded   Content-Disposition  attachment  filename Na C3 AFve 20file txt   In ASP Net I use the following code   string contentDisposition  if  Request Browser Browser     IE   amp  amp   Request Browser Version     7 0     Request Browser Version     8 0        contentDisposition    attachment  filename     Uri EscapeDataString fileName   else if  Request Browser Browser     Safari       contentDisposition    attachment  filename     fileName  else     contentDisposition    attachment  filename  UTF-8      Uri EscapeDataString fileName   Response AddHeader  Content-Disposition   contentDisposition     I tested the above using IE7  IE8  IE9  Chrome 13  Opera 11  FF5  Safari 5   Update November 2013   Here is the code I currently use  I still have to support IE8  so I cannot get rid of the first part  It turns out that browsers on Android use the built in Android download manager and it cannot reliably parse file names in the standard way   string contentDisposition  if  Request Browser Browser     IE   amp  amp   Request Browser Version     7 0     Request Browser Version     8 0        contentDisposition    attachment  filename     Uri EscapeDataString fileName   else if  Request UserAgent    null  amp  amp  Request UserAgent ToLowerInvariant   Contains  android       android built-in download manager  all browsers on android      contentDisposition    attachment  filename       MakeAndroidSafeFileName fileName          else     contentDisposition    attachment  filename       fileName        filename  UTF-8      Uri EscapeDataString fileName   Response AddHeader  Content-Disposition   contentDisposition     The above now tested in IE7-11  Chrome 32  Opera 12  FF25  Safari 6  using this filename for download    abcABC                                                    amp                        -    txt  On IE7 it works for some characters but not all  But who cares about IE7 nowadays   This is the function I use to generate safe file names for Android  Note that I don t know which characters are supported on Android but that I have tested that these work for sure   private static readonly Dictionary lt char  char gt  AndroidAllowedChars    abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ  -                       0123456789  ToDictionary c   gt  c   private string MakeAndroidSafeFileName string fileName        char   newFileName   fileName ToCharArray        for  int i   0  i  lt  newFileName Length  i                  if   AndroidAllowedChars ContainsKey newFileName i                newFileName i                   return new string newFileName        TomZ  I tested in IE7 and IE8 and it turned out that I did not need to escape apostrophe      Do you have an example where it fails    Dave Van den Eynde  Combining the two file names on one line as according to RFC6266 works except for Android and IE7 8 and I have updated the code to reflect this  Thank you for the suggestion    Thilo  No idea about GoodReader or any other non-browser  You might have some luck using the Android approach    Alex Zhukovskiy  I don t know why but as discussed on Connect it doesn t seem to work terribly well

[browser] How to encode the filename parameter of Content-Disposition header in HTTP?

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