multipart/*
multipart/form-data
The HTML form encoding that supports file uploads.
What is multipart/form-data?
multipart/form-data is the Content-Type used by HTML forms that include a file input. Each field is transmitted as its own MIME part with independent headers, which lets binary files travel alongside plain text fields in a single request.
Typical usage
File uploads from HTML forms, chunked uploads, mail attachments.
Common gotchas
The Content-Type header includes a boundary parameter (e.g. `multipart/form-data; boundary=...`). Do not omit the boundary — the request will be rejected.
HTTP header example
Response header
Content-Type: multipart/form-dataReference
RFC 7578
Frequently asked questions
What is the multipart/form-data MIME type?
multipart/form-data is the Content-Type used by HTML forms that include a file input. Each field is transmitted as its own MIME part with independent headers, which lets binary files travel alongside plain text fields in a single request.
What file extension does multipart/form-data use?
multipart/form-data has no single canonical file extension — it is used as a transfer / content type rather than being tied to a specific file name suffix.
How do I set the Content-Type for multipart/form-data?
Send the HTTP response header Content-Type: multipart/form-data. File uploads from HTML forms, chunked uploads, mail attachments.
Is multipart/form-data an official MIME type?
Yes. multipart/form-data is officially registered with IANA (RFC 7578), so standards-conformant clients recognize it.
What are common mistakes with multipart/form-data?
The Content-Type header includes a boundary parameter (e.g. `multipart/form-data; boundary=...`). Do not omit the boundary — the request will be rejected.