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 email, 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), Request header, Response 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).

http

Content-Disposition: inline
Content-Disposition: attachment
Content-Disposition: attachment; filename="filename.jpg"
Content-Disposition: attachment; filename*="filename.jpg"

The quotes around the filename are optional, but are necessary if you use special characters in the filename, such as spaces.

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. It's recommended to include both for maximum compatibility, and you can convert filename* to filename by substituting non-ASCII characters with ASCII equivalents (such as converting é to e). You may want to avoid percent escape sequences in filename, because they are handled inconsistently across browsers. (Firefox and Chrome decode them, while Safari does not.)

Browsers may apply transformations to conform to the file system requirements, such as converting path separators (/ and \) to underscores (_).

Note: 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 semicolon (';').

http

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. This parameter provides mostly indicative information. The suggestions in RFC2183 apply:

Prefer ASCII characters if possible (the client may percent-encode it, as long as the server implementation decodes it).
Any path information should be stripped, such as by replacing / with _.
When writing to disk, it should not overwrite an existing file.
Avoid creating special files with security implications, such as creating a file on the command search path.
Satisfy other file system requirements, such as restricted characters and length limits.

Note that the request header does not have the filename* parameter and does not allow RFC 5987 encoding.

Examples

A response triggering the "Save As" dialog:

http

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:

http

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

Specification
Use of the Content-Disposition Header Field in the Hypertext Transfer Protocol (HTTP) # header.field.definition
Returning Values from Forms: multipart/form-data # section-4.2

Browser compatibility

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