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

321
votes

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?

4
httphttp-headershttprequestcontent-type
Valid media types are supposed to be registered with the IANA - you can see a current list here: iana.org/assignments/media-types/media-types.xhtml but note this list can update over time. There is not a fixed allowed list. – Joe
Related post - ASP MVC - Are there any constants for the default content types? – RBT
@Joe: "Valid media types are supposed to be registered with the IANA" - wait, does this mean custom media types (only for use in an application-specific web API that is only going to be called by a custom client application) are not permitted at all? – O. R. Mapper
@O.R.Mapper i'd read it more as "there is an official list, but i would not be surprised to see lots of others in the wild". In terms of the OP's question, if you were going to try and validate "all types" you'd at least want to validate all registered types. What to do with additional ones is more open-ended. As far as I know there is no requirement to register custom types. – Joe
Please accept the answer which helped you most in solving your problem. It helps future readers. If the answers weren't helpful leave comments below them. So the poster can update them accordingly. Read What should I do when someone answers my question? to know more. – Roshana Pitigala

4 Answers

338
votes

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
53
votes

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.

3
votes

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.

0
votes

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.