ContentDisposition

ContentDisposition refers to the Content-Disposition header field used in MIME and HTTP to describe how content should be handled or presented by a user agent. In HTTP responses, this header guides how the payload is treated by the browser: inline suggests the content can be displayed within the page, while attachment indicates the content should be offered for download or saved to disk. A filename parameter may accompany these directives to suggest a default file name, for example, Content-Disposition: attachment; filename="report.pdf". Values are typically tokens or quoted strings, and non-ASCII names can be conveyed using encoded forms such as filename* per related standards.

In multipart/form-data, which is used for form submissions that include file uploads, Content-Disposition appears on each part. A common form is form-data; name="field"; filename="example.txt", where the name parameter identifies the form field and the filename parameter provides the client-supplied file name. The part may also include a Content-Type for the uploaded file.

Standards and evolution: The header field originated in MIME with RFC 2183 and was later updated for HTTP use in RFC 6266. For form uploads, the multipart/form-data semantics are described in RFC 2388. Real-world usage varies across clients and servers, especially regarding encoding of non-ASCII filenames and cross-browser compatibility.

Practical considerations include correct handling of quoted parameters, safe and sanitized filenames, and awareness of how different user agents may honor or override the directives when downloading or displaying content.