Content-Disposition
source link: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Disposition
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Content-Disposition
In a regular HTTP response, the Content-Disposition
response header is a header indicating if the content is expected to be displayed inline in the browser, that is, as a Web page or as part of a Web page, or as an attachment, that is downloaded and saved locally.
In a multipart/form-data
body, the HTTP Content-Disposition
general header is a header that must be used on each subpart of a multipart body to give information about the field it applies to. The subpart is delimited by the boundary defined in the Content-Type
header. Used on the body itself, Content-Disposition
has no effect.
The Content-Disposition
header is defined in the larger context of MIME messages for e-mail, but only a subset of the possible parameters apply to HTTP forms and POST
requests. Only the value form-data
, as well as the optional directive name
and filename
, can be used in the HTTP context.
Header type
Response header (for the main body)
General header (for a subpart of a multipart body)
Forbidden header name
no
Syntax
As a response header for the main body
The first parameter in the HTTP context is either inline
(default value, indicating it can be displayed inside the Web page, or as the Web page) or attachment
(indicating it should be downloaded; most browsers presenting a 'Save as' dialog, prefilled with the value of the filename
parameters if present).
Content-Disposition: inline Content-Disposition: attachment Content-Disposition: attachment; filename="filename.jpg"
Notes: Chrome, and Firefox 82 and later, prioritize the HTML <a> element's download
attribute over the Content-Disposition
inline
parameter (for same-origin URLs). Earlier Firefox versions prioritize the header and will display the content inline.
As a header for a multipart body
A multipart/form-data
body requires a Content-Disposition
header to provide information for each subpart of the form (e.g. for every form field and any files that are part of field data). The first directive is always form-data
, and the header must also include a name
parameter to identify the relevant field. Additional directives are case-insensitive and have arguments that use quoted-string syntax after the '='
sign. Multiple parameters are separated by a semi-colon (';'
).
Content-Disposition: form-data; name="fieldName" Content-Disposition: form-data; name="fieldName"; filename="filename.jpg"
Directives
name
Is followed by a string containing the name of the HTML field in the form that the content of this subpart refers to. When dealing with multiple files in the same field (for example, the multiple
attribute of an <input type="file">
element), there can be several subparts with the same name.
A name
with a value of '_charset_'
indicates that the part is not an HTML field, but the default charset to use for parts without explicit charset information.
filename
Is followed by a string containing the original name of the file transmitted. The filename is always optional and must not be used blindly by the application: path information should be stripped, and conversion to the server file system rules should be done. This parameter provides mostly indicative information. When used in combination with Content-Disposition: attachment
, it is used as the default filename for an eventual "Save As" dialog presented to the user.
filename*
The parameters filename
and filename*
differ only in that filename*
uses the encoding defined in RFC 5987. When both filename
and filename*
are present in a single header field value, filename*
is preferred over filename
when both are understood.
The string following filename
should always be put into quotes; but, for compatibility reasons, many browsers try to parse unquoted names that contain spaces.
Examples
A response triggering the "Save As" dialog:
200 OK Content-Type: text/html; charset=utf-8 Content-Disposition: attachment; filename="cool.html" Content-Length: 21 <HTML>Save me!</HTML>
This simple HTML file will be saved as a regular download rather than displayed in the browser. Most browsers will propose to save it under the cool.html
filename (by default).
An example of an HTML form posted using the multipart/form-data
format that makes use of the Content-Disposition
header:
POST /test.html HTTP/1.1 Host: example.org Content-Type: multipart/form-data;boundary="boundary" --boundary Content-Disposition: form-data; name="field1" value1 --boundary Content-Disposition: form-data; name="field2"; filename="example.txt" value2 --boundary--
Specifications
Browser compatibility
Report problems with this data on GitHubContent-Disposition
Legend
Compatibility notes
- Firefox 5 handles the
Content-Disposition
HTTP response header more effectively if both thefilename
andfilename*
parameters are provided; it looks through all provided names, using thefilename*
parameter if one is available, even if afilename
parameter is included first. Previously, the first matching parameter would be used, thereby preventing a more appropriate name from being used. See bug 588781. - Firefox 82 (and later) and Chrome prioritize the HTML <a> element's
download
attribute over theContent-Disposition
inline
parameter (for same-origin URLs). Earlier Firefox versions prioritize the header and will display the content inline.
See also
- HTML Forms
- The
Content-Type
defining the boundary of the multipart body. - The
FormData
interface used to manipulate form data for use in theXMLHttpRequest
API.
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