How to Send HTTP POST Requests with cURL: Working Code Examples

Need a reliable curl post example to interact with APIs? You might be testing endpoints or automating requests. cURL provides a powerful way to send data over HTTP.

The -d or --data parameter lets you include specific data in POST requests. This flexibility makes cURL an ideal tool for API testing and development. Most APIs work with two common data formats: application/json and application/x-www-form-urlencoded. Many developers prefer the form urlencoded format on the command line because JSON needs extra quoting and explicit Content-Type headers.

This piece will show you practical curl post request examples you can use right away. We'll cover the simple syntax and show you the quickest way to handle curl post data. You'll learn about curl post body parameters and see how to create curl post with body content. The guide also includes curl post json examples that will help you become skilled at API interactions.

Basic Syntax for Sending POST Requests with cURL

The basic syntax of POST requests with cURL follows a simple pattern. POST operations differ from GET requests because they send data separately from the URL, which keeps it hidden from the address field.

You can send a POST request most simply by using:

curl -d "param1=value1&param2=value2" http://example.com/

Adding -X POST explicitly to specify the POST method isn't needed when you use the -d flag. cURL automatically picks POST as the HTTP method whenever you pass data through the -d option.

Data parameters can also be split using multiple -d flags:

curl -d name=admin -d shoesize=12 http://example.com/

cURL smartly joins these parameters by adding ampersands between them.

Larger data sets can be handled by reading content straight from a file:

curl -d @filename http://example.com/

The -d flag skips carriage returns and newlines while reading files. You should use --data-binary instead if these characters need to be included.

Data starting with the @ symbol requires --data-raw to stop cURL from treating it as a filename.

Sending Data in POST Requests

cURL offers different ways to transmit data in POST requests. Each method has unique advantages that depend on your needs.

The -d option sends form-encoded data (the default content type):

curl --data 'name=michael' http://example.com/my-form/

JSON data requires an explicit header setting:

curl --header "Content-Type: application/json" 
--request POST --data '{"name":"michael","value":"123"}' 
https://example.com/api/

Windows command line users need special JSON serialization with escaped quotes:

curl --header "Content-Type: application/json" --data 
"{\"emailAddress\":\"user@example.com\"}" 
https://example.com/api/

File contents can be uploaded using the @ symbol before the filename:

curl --data @myfilename https://example.com/api/

The standard --data option strips carriage returns and newlines from files. You can use --data-binary to preserve formatting in raw file content:

curl --data-binary @1.txt https://example.com/api/

The -F option handles multipart form uploads effectively:

curl -F files=@1.txt https://example.com/api/

You can also specify MIME types for uploaded files:

curl -F 'file=@path/to/file.csv;type=text/csv' https://example.com/api/

Working with JSON and Custom Headers

JSON data exchange is the foundation of most modern API interactions. The correct Content-Type header is vital when sending JSON with cURL because cURL defaults to application/x-www-form-urlencoded with the -d option.

You need to define your headers explicitly using the standard approach:

curl -H "Content-Type: application/json" -X POST -d '{"name":"value"}' https://example.com/

The convenient --json option in curl 7.82.0 and newer makes this process simpler by setting appropriate JSON headers automatically:

curl --json '{"tool": "curl"}' https://example.com/

This single flag replaces three separate options: --data-binary, Content-Type: application/json header, and Accept: application/json header.

You can read larger JSON payloads directly from files:

curl --json @data.json https://example.com/

JSON quoting needs special attention on Windows systems - double quotes must be escaped:

curl -H "Content-Type: application/json" -d "{\"key\":\"value\"}" https://example.com/

Your productivity improves when you combine cURL with specialized JSON tools. The jo tool generates JSON and jq processes responses:

jo name=value | curl --json @- https://example.com/ | jq

The -g option in cURL prevents URL globbing issues when your JSON contains special characters like braces or brackets.

Conclusion

cURL stands out as a powerful tool for sending HTTP POST requests. This command-line utility comes with many options to handle different data formats and requirements. Developers working with APIs find it indispensable.

The -d flag in the basic syntax triggers the POST method automatically. You don't need to declare it explicitly. The tool offers several ways to send data, from simple name-value pairs to complex JSON structures.

Form-encoded data is simple to implement. JSON requests need proper header configuration. The newer cURL versions make this process easier with the --json option. This feature replaces what used to take multiple separate commands.

File uploads showcase another key feature. You can send file contents directly or as multipart form data. Your terminal becomes a testing ground for almost any API endpoint.

Platform differences play a role in crafting cURL commands. Windows systems need special attention with quote escaping. Understanding these details helps create scripts that work in any environment.

The examples in this piece serve as templates you can use right away. They cover common scenarios when working with web services. Instead of remembering all options, you can adapt these patterns to your needs.

cURL gives you a reliable way to check request-response patterns without complex setup. It helps when testing new API endpoints or fixing integration issues. These techniques will boost your development workflow and debugging skills.

FAQs

What is the basic syntax for sending a POST request with cURL?

The basic syntax for sending a POST request with cURL is: curl -d "param1=value1&param2=value2" http://example.com/. This command sends form-encoded data to the specified URL using the POST method.

How can I send JSON data in a POST request using cURL?

To send JSON data in a POST request, use the following syntax: curl -H "Content-Type: application/json" -X POST -d '{"name":"value"}' https://example.com/. This sets the appropriate Content-Type header and includes the JSON data in the request body.

Can I send data from a file using cURL?

Yes, you can send data from a file using cURL. Use the @ symbol before the filename like this: curl -d @filename http://example.com/. This reads the content of the file and sends it as the request body.

How do I handle multipart form uploads with cURL?

For multipart form uploads, especially useful with files, use the -F option. For example: curl -F files=@1.txt https://example.com/api/. This allows you to upload files as part of a multipart form request.

Is there an easier way to send JSON data in newer versions of cURL?

Yes, in cURL version 7.82.0 and newer, you can use the --json option to simplify sending JSON data. For example: curl --json '{"tool": "curl"}' https://example.com/. This automatically sets the appropriate JSON headers and sends the data in the correct format.

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curl -d name=admin -d shoesize=12 http://example.com/

cURL smartly joins these parameters by adding ampersands between them.

Larger data sets can be handled by reading content straight from a file:

curl -d @filename http://example.com/

The -d flag skips carriage returns and newlines while reading files. You should use --data-binary instead if these characters need to be included.

Data starting with the @ symbol requires --data-raw to stop cURL from treating it as a filename.

Sending Data in POST Requests

cURL offers different ways to transmit data in POST requests. Each method has unique advantages that depend on your needs.

The -d option sends form-encoded data (the default content type):

curl --data 'name=michael' http://example.com/my-form/

JSON data requires an explicit header setting:

curl --header "Content-Type: application/json" --request POST --data 
'{"name":"michael","value":"123"}' 
https://example.com/api/

Windows command line users need special JSON serialization with escaped quotes:

curl --header "Content-Type: application/json" --data 
"{\"emailAddress\":\"user@example.com\"}" 
https://example.com/api/

File contents can be uploaded using the @ symbol before the filename:

curl --data @myfilename https://example.com/api/

The standard --data option strips carriage returns and newlines from files. You can use --data-binary to preserve formatting in raw file content:

curl --data-binary @1.txt https://example.com/api/

The -F option handles multipart form uploads effectively:

curl -F files=@1.txt https://example.com/api/

You can also specify MIME types for uploaded files:

curl -F 'file=@path/to/file.csv;type=text/csv' https://example.com/api/

Working with JSON and Custom Headers

JSON data exchange is the foundation of most modern API interactions. The correct Content-Type header is vital when sending JSON with cURL because cURL defaults to application/x-www-form-urlencoded with the -d option.

You need to define your headers explicitly using the standard approach:

curl -H "Content-Type: application/json" -X POST -d '{"name":"value"}' https://example.com/

The convenient --json option in curl 7.82.0 and newer makes this process simpler by setting appropriate JSON headers automatically:

curl --json '{"tool": "curl"}' https://example.com/

This single flag replaces three separate options: --data-binary, Content-Type: application/json header, and Accept: application/json header.

You can read larger JSON payloads directly from files:

curl --json @data.json https://example.com/

JSON quoting needs special attention on Windows systems - double quotes must be escaped:

curl -H "Content-Type: application/json" -d "{\"key\":\"value\"}" https://example.com/

Your productivity improves when you combine cURL with specialized JSON tools. The jo tool generates JSON and jq processes responses:

jo name=value | curl --json @- https://example.com/ | jq

The -g option in cURL prevents URL globbing issues when your JSON contains special characters like braces or brackets.

Conclusion

cURL stands out as a powerful tool for sending HTTP POST requests. This command-line utility comes with many options to handle different data formats and requirements. Developers working with APIs find it indispensable.

The -d flag in the basic syntax triggers the POST method automatically. You don't need to declare it explicitly. The tool offers several ways to send data, from simple name-value pairs to complex JSON structures.

Form-encoded data is simple to implement. JSON requests need proper header configuration. The newer cURL versions make this process easier with the --json option. This feature replaces what used to take multiple separate commands.

File uploads showcase another key feature. You can send file contents directly or as multipart form data. Your terminal becomes a testing ground for almost any API endpoint.

Platform differences play a role in crafting cURL commands. Windows systems need special attention with quote escaping. Understanding these details helps create scripts that work in any environment.

The examples in this piece serve as templates you can use right away. They cover common scenarios when working with web services. Instead of remembering all options, you can adapt these patterns to your needs.

cURL gives you a reliable way to check request-response patterns without complex setup. It helps when testing new API endpoints or fixing integration issues. These techniques will boost your development workflow and debugging skills.

FAQs

What is the basic syntax for sending a POST request with cURL?

The basic syntax for sending a POST request with cURL is: curl -d "param1=value1&param2=value2" http://example.com/. This command sends form-encoded data to the specified URL using the POST method.

How can I send JSON data in a POST request using cURL?

To send JSON data in a POST request, use the following syntax: curl -H "Content-Type: application/json" -X POST -d '{"name":"value"}' https://example.com/. This sets the appropriate Content-Type header and includes the JSON data in the request body.

Can I send data from a file using cURL?

Yes, you can send data from a file using cURL. Use the @ symbol before the filename like this: curl -d @filename http://example.com/. This reads the content of the file and sends it as the request body.

How do I handle multipart form uploads with cURL?

For multipart form uploads, especially useful with files, use the -F option. For example: curl -F files=@1.txt https://example.com/api/. This allows you to upload files as part of a multipart form request.

Is there an easier way to send JSON data in newer versions of cURL?

Yes, in cURL version 7.82.0 and newer, you can use the --json option to simplify sending JSON data. For example: curl --json '{"tool": "curl"}' https://example.com/. This automatically sets the appropriate JSON headers and sends the data in the correct format.