What are all the possible values for HTTP "Content-Type" header?

I have to validate the Content-Type header value before passing it to an HTTP request.

Is there a specific list for all the possible values of Content-Type?

Otherwise, is there a way to validate the content type before using it in an HTTP request?

You can find every content type here: http://www.iana.org/assignments/media-types/media-types.xhtml

The most common type are:

1. Type application

    application/java-archive
    application/EDI-X12   
    application/EDIFACT   
    application/javascript   
    application/octet-stream   
    application/ogg   
    application/pdf  
    application/xhtml+xml   
    application/x-shockwave-flash    
    application/json  
    application/ld+json  
    application/xml   
    application/zip  
    application/x-www-form-urlencoded  
   

2. Type audio

    audio/mpeg   
    audio/x-ms-wma   
    audio/vnd.rn-realaudio   
    audio/x-wav   
   

3. Type image

    image/gif   
    image/jpeg   
    image/png   
    image/tiff    
    image/vnd.microsoft.icon    
    image/x-icon   
    image/vnd.djvu   
    image/svg+xml    
   

4. Type multipart

    multipart/mixed    
    multipart/alternative   
    multipart/related (using by MHTML (HTML mail).)  
    multipart/form-data  
   

5. Type text

    text/css    
    text/csv    
    text/html    
    text/javascript (obsolete)    
    text/plain    
    text/xml    
   

6. Type video

    video/mpeg    
    video/mp4    
    video/quicktime    
    video/x-ms-wmv    
    video/x-msvideo    
    video/x-flv   
    video/webm   
   

7. Type vnd :

    application/vnd.android.package-archive
    application/vnd.oasis.opendocument.text    
    application/vnd.oasis.opendocument.spreadsheet  
    application/vnd.oasis.opendocument.presentation   
    application/vnd.oasis.opendocument.graphics   
    application/vnd.ms-excel    
    application/vnd.openxmlformats-officedocument.spreadsheetml.sheet   
    application/vnd.ms-powerpoint    
    application/vnd.openxmlformats-officedocument.presentationml.presentation    
    application/msword   
    application/vnd.openxmlformats-officedocument.wordprocessingml.document   
    application/vnd.mozilla.xul+xml   
   

As is defined in RFC 1341:

> In the Extended BNF notation of RFC 822, a Content-Type header field > value is defined as follows: > > Content-Type := type "/" subtype [";" parameter] > > type := "application" / "audio" > / "image" / "message" > / "multipart" / "text" > / "video" / x-token > > x-token := < The two characters "X-" followed, with no > intervening white space, by any token > > > subtype := token > > parameter := attribute "=" value > > attribute := token > > value := token / quoted-string > > token := 1 > > tspecials := "(" / ")" / "<" / ">" / "@" ; Must be in > / "," / ";" / ":" / "" / <"> ; quoted-string, > / "/" / "[" / "]" / "?" / "." ; to use within > / "=" ; parameter values

And a list of known MIME types that can follow it (or, as Joe remarks, the IANA source).

As you can see the list is way too big for you to validate against all of them. What you can do is validate against the general format and the type attribute to make sure that is correct (the set of options is small) and just assume that what follows it is correct (and of course catch any exceptions you might encounter when you put it to actual use).

Also note the comment above:

> If another primary type is to be used for any reason, it must be given a name starting with "X-" to indicate its non-standard status and to avoid any potential conflict with a future official name.

You'll notice that a lot of HTTP requests/responses include an X- header of some sort which are self defined, keep this in mind when validating the types.

I would aim at covering a subset of possible "Content-type" values, you question seems to focus on identifying known content types.

@Jeroen RFC 1341 reference is great, but for an fairly exhaustive list IANA keeps a web page of officially registered media types here.

If you are using jaxrs or any other, then there will be a class called mediatype.User interceptor before sending the request and compare it against this.