What is the cURL command-line syntax to do a POST request?

If you are lazy, you can get google-chrome or firefox to do all the work for you.

1. Right-click the form you want to submit and select Inspect (or Inspect Element for Firefox). This will open the DevTools panel.
2. Select the Network tab in devtools and tick the Preserve log checkbox (Persist Logs for firefox).
3. Submit the form and locate the entry with method POST (right-click on any column header and make sure Method is checked).
4. Right click the line with POST, and select Copy > Copy as cURL.

Chrome will copy all the request data in cURL syntax.

Chrome uses --data 'param1=hello&param2=world' which you can make more readable by using a single -d or -F per parameter depending on which type of POST request you want to send, which can be either application/x-www-form-urlencoded or multipart/form-data accordingly.

This will be POST-ed as application/x-www-form-urlencoded (used for the majority of forms that don't contain file uploads):

curl http://httpbin.org/post 
    -H "User-Agent: Mozilla/2.2" 
    -d param1=hello 
    -d name=dinsdale

For a multipart/form-data POST use -F (typically used with forms that contain file uploads, or where order of fields is important, or where multiple fields with the same name are required):

curl http://httpbin.org/post 
    -H "User-Agent: Mozilla/2.2" 
    -F param1=hello 
    -F name=dinsdale 
    -F name=piranha

^{The User-Agent header is not normally needed, but I've thrown it in just in case. If you need a custom agent then you can avoid having to set it on every request by creating the ~/.curlrc file which contains e.g. User-Agent: "Mozilla/2.2"}

Data from stdin with -d @-

Example:

echo '{"text": "Hello **world**!"}' | curl -d @- https://api.github.com/markdown

Output:

<p>Hello <strong>world</strong>!</p>

If you want to login to a site, do the following:

curl -d "username=admin&password=admin&submit=Login" --dump-header headers http://localhost/Login
curl -L -b headers http://localhost/

The first request saves the session cookie (that is provided upon successful login) in the "headers" file. From now on you can use that cookie to authenticate you to any part of the website that you usually access after logging in with a browser.

For a RESTful HTTP POST containing XML:

curl -X POST -d @filename.txt http://example.com/path/to/resource --header "Content-Type:text/xml"

or for JSON, use this:

curl -X POST -d @filename.txt http://example.com/path/to/resource --header "Content-Type:application/json"

This will read the contents of the file named filename.txt and send it as the post request.

With fields:

curl --data "param1=value1&param2=value2" https://example.com/resource.cgi

With fields specified individually:

curl --data "param1=value1" --data "param2=value2" https://example.com/resource.cgi

Multipart:

curl --form "[email protected]" https://example.com/resource.cgi

Multipart with fields and a filename:

curl --form "[email protected];filename=desired-filename.txt" --form param1=value1 --form param2=value2 https://example.com/resource.cgi

Without data:

curl --data '' https://example.com/resource.cgi
    
curl -X POST https://example.com/resource.cgi

curl --request POST https://example.com/resource.cgi

For more information see the cURL manual. The cURL tutorial on emulating a web browser is helpful.

With libcurl, use the curl_formadd() function to build your form before submitting it in the usual way. See the libcurl documentation for more information.

For large files, consider adding parameters to show upload progress:

curl --tr-encoding -X POST -v -# -o output -T filename.dat 
      http://example.com/resource.cgi

The -o output is required, otherwise, no progress bar will appear.

curl -v --data-ascii var=value http://example.com

and there are many more options, check curl --help for more information.

curl -d "name=Rafael%20Sagula&phone=3320780" http://www.where.com/guest.cgi 

is the example found in the Curl Example Manual.

Use %26 for the ampersands though if the above doesn't work:

curl -d "name=Rafael%20Sagula%26phone=3320780" http://www.where.com/guest.cgi