What Is the cURL Command?
cURL is a command-line tool used to transfer data from URLs. It also supports a large variety of network protocols, assists developers in testing and automating information exchange, and debugging network connections. cURL is a powerful tool that can be used by a developer and system administrator, whether they are transferring files, issuing a call to an HTTP interface in a command line, or ensuring their response satisfies the requirements.
What is cURL?
cURL stands for “Client URL.” It is an open-source tool and a library that can be used to transfer data between a client and a server. It is built on top of libcurl integration and supports most protocols, such as HTTP, HTTPS, FTP, etc. It is used in automated scripting by developers to automate transfers of information to URLs, manipulate authentication and make quick searches of servers. Since it can run directly through the terminal, cURL is useful in API testing and auto tests.
How Does cURL Work?
cURL works by sending a request from your terminal to a server and printing the server’s response back to you. When you run a command, cURL opens a connection to the URL, sends the chosen HTTP method and any headers or data, and waits for the reply. It then returns the response — a web page, an API result, or a file — directly in the command line or saves it to disk.
Because it runs as a single command, cURL is easy to drop into scripts, scheduled jobs, and automated tests. You do not need a browser or a graphical client to send a request, which is why developers use it to test APIs, download files, and check how a server responds.
What Does the cURL Command Do?
A cURL request transfers or obtains information to a particular URL. It is able to make web page requests, command-line HTTP requests, multipart file uploads, or API endpoint testing. Some developers run a cURL request to check the response of a server to the information submitted using different HTTP commands like GET, POST, PUT, or DELETE, and to perform SSL handshake verification for secure connections.
cURL Command Syntax
The basic syntax of a cURL command follows a simple pattern:
curl [options] [URL]
The curl keyword starts the command, the options (such as -i or -d) control how the request behaves, and the URL is the address you want to reach. Options and the URL can be combined in almost any order, and you can use several options in a single request. If you run curl with a URL and no options, cURL sends a simple GET request and prints the response body.
Common cURL Commands and Options
cURL options (also called flags or parameters) change how a request is sent and what cURL returns. You add them after the curl keyword and before the URL. Below are the options developers use most often.
| Option | What it does | Example |
-i | Includes the response headers in the output, along with the body | curl -i https://api.example.com |
-d | Sends data in the request body (turns the request into a POST by default) | curl -d "name=test" https://api.example.com |
-X | Sets the HTTP method, such as GET, POST, PUT or DELETE | curl -X POST https://api.example.com |
-H | Adds a custom request header | curl -H "Authorization: Bearer TOKEN" https://api.example.com |
-o | Saves the output to a file with a name you choose | curl -o page.html https://example.com |
-O | Saves the output using the remote file’s own name | curl -O https://example.com/file.zip |
-L | Follows redirects to the final URL | curl -L https://example.com |
-u | Passes a username and password for authentication | curl -u user:pass https://api.example.com |
-s | Runs in silent mode and hides progress and error output | curl -s https://example.com |
-v | Enables verbose mode to debug the full request and response | curl -v https://example.com |
-k | Allows insecure connections by skipping the SSL certificate check | curl -k https://example.com |
-f | Fails quietly on server errors instead of printing the error page | curl -f https://example.com |
To see the full list of options at any time, run curl -h (or curl --help) in the terminal.
What Does curl -i Do?
The -i option tells cURL to include the response headers in the output together with the body. Instead of returning only the page or API response, cURL prints the HTTP status line, headers like Content-Type and Set-Cookie, and then the body. It is useful when you need to check what a server actually returns, debug an API, or confirm a status code.
curl -i https://api.example.com/data
Use -I (uppercase) if you want only the headers and not the body.
cURL Usage
cURL is free to download when send commands at the CLI. This tool makes testing, information transfer, and automation of server communication easy. cURL can also work through proxy servers by routing requests via specified proxy addresses, enabling secure connections and authentication when accessing restricted networks.
cURL Command Examples
Here are common cURL commands you can copy and adapt:
| Task | Command |
| Send a basic GET request | curl https://api.example.com/data |
| Send a POST request with data | curl -d "user=test&id=1" https://api.example.com |
| View response headers and body | curl -i https://api.example.com/data |
| Save the response to a file | curl -o result.json https://api.example.com/data |
| Follow redirects | curl -L https://example.com |
| Send a request with authentication | curl -u user:pass https://api.example.com |
| Debug a request in detail | curl -v https://api.example.com |
You can also send GET requests with cURL or route cURL through a proxy when you need to test from a different location or IP.
cURL vs wget
In short: reach for cURL when you need to interact with an API or inspect a response, and for wget when your main goal is downloading files in bulk.
cURL and wget are both command-line tools for transferring data, but they serve slightly different needs. cURL is built around sending requests and reading responses, which makes it the go-to choice for API testing, custom headers, and authentication. wget is built around downloading files and can follow links to download whole sites, which makes it stronger for recursive downloads.
FAQs
What does cURL stand for?
cURL stands for “Client URL.” It is an open-source command-line tool and library (libcurl) for transferring data to and from a URL.
What is the cURL command used for?
It is used to send and receive data over the network — testing APIs, downloading files, sending HTTP requests, checking server responses, and automating these tasks inside scripts.
Is cURL free to use?
Yes. cURL is free and open-source, and it comes pre-installed on most macOS and Linux systems and on modern versions of Windows.
What does curl -k do?
The -k option lets cURL connect to a server even if its SSL certificate cannot be verified. It is handy for local testing but should be avoided in production because it skips a security check.
What does curl -s do?
The -s (silent) option hides the progress meter and error messages, so cURL prints only the response. It is often used in scripts to keep the output clean.
How do I run a cURL command?
Open a terminal (Command Prompt or PowerShell on Windows, Terminal on macOS and Linux), type your curl command, and press Enter. cURL prints the result directly in the terminal.