How to Use cURL with a Proxy?

This article offers a short guide on using cURL with a proxy server.

What is cURL?

cURL is a command line tool that transfers data to or from a server; it is necessary for API testing, file downloading, and many other tasks.

In simple terms, cURL is a "client URL".

A typical URL structure looks like this:

<protocol_or_scheme>://<username>:<password>@<host>:<port>/<path>?<additional_parameters>#<anchor>

If certain elements are not used, they are omitted (removed from the URL). Here's how URL addresses look for the well-known HTTP protocol:

http://www.domain.zone/path/to/page/

cURL supports the following protocols:

HTTP and its secure HTTPS, GOPHER version (similar to www);
For handling FTP (FTPS), SFTP, FILE, TFTP, LDAP (LDAPS) files;
For remote connections SCP, SMB, SMBS, TELNET;
For mail operations POP3 (POP3S), IMAP (IMAPS), SMTP (SMTPS);
As well as DICT, RTMP and RTSP.

The most pleasant aspect, however, is that curl HTTP proxy and curl SOCKS proxy options are also available.

cURL supports HTTP and SOCKS proxies, which is very important when you must hide your IP address or bypass network restrictions and connect through a proxy.

cURL Compatibility with Various OS

Windows

All recent versions of Windows OS (operating systems) starting from the one created in 1803 (Windows 10) and above come with the built-in cURL client. However, there are nuances. The system solution works similarly to the Invoke-WebRequest cmdlet. Consequently, it assumes the use of modified syntax, which makes many command-line parameters unavailable.

Therefore, if you want to use the standard cURL interface, you'll need to choose one of several solutions:

Direct access to the curl.exe file (you can download the latest cURL version for Windows from the official utility website);
Installation of the Windows Subsystem for Linux (WSL), which essentially serves as a specialized virtual machine;
Manual installation of any Linux distribution in a virtualization environment (VirtualBox and its analogs).

Linux

cURL installation is generally unnecessary in most cases. In all popular distributions, the conjunction of the library and utility is available by default.

If the system displays an error about the missing executable file when invoking the curl command in the terminal, you can install the program using the standard package manager, for example:

For Debian/Ubuntu-based distributions – sudo apt-get install curl
For Fedora/CentOS/RHEL-based distributions – yum install curl
For ArchLinux-based distributions – pacman -Sy curl

macOS

cURL is installed in all macOS versions by default. To start using the utility, simply open the "Terminal" application and start entering commands.

The following section will provide a short guide to installing and using cURL with a proxy.

Using cURL with a Proxy

This guide will help you quickly configure cURL to work with different types of proxies for secure, private, or limited connections.

To use cURL from the command line, follow these steps:

Determine whether your proxy is HTTP, HTTPS, or SOCKS5. This will affect the command syntax you use in cURL.
To open the command line, press the keyboard shortcut "Win + R" (Windows), "Ctrl + Alt + T" (Linux), or press the terminal button on your device (macOS).
In the window that appears, type "cmd" and click OK.
In the command line that appears, include the -x or --proxy option, then the proxy type and address as follows, replacing proxy_ip and port with the actual IP address and port of your proxy:
To use SOCKS5 with cURL, specify socks5:// before the proxy address:
If your proxy requires authentication, use the -U option to enter the username and password:
Run the command, and cURL will use the specified proxy to connect. Check the response headers or IP information to verify it uses a proxy.
To work further with cURL with a proxy, you need to know the basic list of arguments because the command without arguments will give no result. To see the basic list of available arguments, enter the command in the terminal:
```
curl --help
```
To get the most complete overview of all options, enter the command:
```
curl --help all--help all
```

The list of general cURL arguments includes:

Tools for tracing and sending requests.
Fine-tuning for managing SSL certificates and authentication methods.
Tools for working with file downloads, cookies, sessions, IP protocols etc.
Means for sending data.
Writing data to files (to store received information).
Control over encodings, timing, and connection speeds.
Detailed work with proxies and tunneling.

With this utility alone, you can gather and retrieve headers from target website pages download their entire content, including HTML pages. All you need is a console and a few standard commands.

If you still have any questions about the operation of our service froxy.com, you can ask them in the online chat in the lower right corner of the site or contact support at support@froxy.com.