TopolearnCreating and updating resources means sending request bodies, and getting encoding right avoids subtle bugs.
-d (or --data) sends a request body and switches the method to POST, with Content-Type: application/x-www-form-urlencoded:
curl -d 'name=Ann&age=30' https://example.com/users
Body variants:
-d @filereads the body from a file, but strips newlines. Use--data-binary @fileto send a file byte for byte.--data-urlencode 'q=a b&c'URL-encodes the value for you (sendsq=a+b%26c), safer for user input.- Multiple
-doptions are joined with&.
-F builds a multipart/form-data body, like an HTML form with a file input: -F 'title=Report' -F 'file=@report.pdf'. Add ;type=application/pdf to set a part's content type.
-X sets the method name: -X PUT -d ..., -X DELETE, -X PATCH -d .... It changes only the word in the request line; the body still comes from -d. You do not need -X POST with -d (it is already POST), and -X with -L keeps that method on every redirect, which is often wrong. Never use -X HEAD; use -I.
-G turns -d data into a query string on a GET, convenient for search APIs: curl -G --data-urlencode 'q=rust lang' https://api.example.com/search.
Example
curl -d 'name=Ann&age=30' https://api.example.com/form
# body: name=Ann&age=30 Content-Type: application/x-www-form-urlencoded
curl --data-urlencode 'q=a b&c' https://api.example.com/s
# body: q=a+b%26c
curl --data-binary @payload.xml -H 'Content-Type: application/xml' https://api.example.com/import
curl -F 'title=Q3 report' -F 'file=@report.pdf;type=application/pdf' https://api.example.com/upload
curl -X PUT -d 'status=done' https://api.example.com/tasks/7
curl -X DELETE https://api.example.com/tasks/7
curl -G --data-urlencode 'q=rust lang' https://api.example.com/search # GET ?q=rust+langRemember
- -d sends form-encoded POST; --data-binary @file preserves bytes
- -F makes multipart uploads; @file attaches a file
- -X only renames the method; -G moves -d data into the query string
Watch out for
- Sending a JSON file with -d @file.json: newlines are stripped and the Content-Type is wrong.