What is a cURL?

What is cURL

If this is the first time you hear about cURL, you’ll be surprised to learn that cURL is very widespread. If you use a device to transfer any data through the internet – cURL is hidden in there somewhere. So yes, if you are using the internet, you are bound to run into these.

Say you are doing competitor analysis, lead generation, or market research and want to collect data remotely—you’ll need to understand the connection between cURL and a proxy (a service that can mask your IP address). We’ll explain this connection in a bit. 

Despite this widespread presence of cURLs, people still know very little about them, and the internet is full of FAQs about what cURL is and how to use it. That’s why we’ve composed a straightforward guide to help you learn all about the mysteries of cURL by defining the term and giving some examples of its use.


What is a client URL?

cURL stands for client URL and acts as a cross-platform library and an open-source line tool for commands to transfer data among servers. cURL is distributed among the majority, if not all, operating systems.

Wherever an internet protocol involves sending or receiving data, cURL programming is present. The history of cURL is not very complicated. In the 90s, Daniel Sternberg wanted to create an IRC script that could convert different currencies for members of a chat group.

In 1997, programmers wrote only a couple of hundred HTTP code lines, which became the foundation for cURL. It finally got its name in 1998 as cURL 3.0. 

The main task of a cURL is to transfer data that goes through internet protocols. Everything other than the transfer is not under the scope of cURL. Therefore, cURL doesn’t have anything to do with the transferred data, just its transfer process.

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Common issues & uses of cURL

Client URL is a powerful tool when used for transferring data through internet protocols. We’ll mention the most common use cases of cURL that make things easier for our data transfers:

  1. Sending POST requests

If we are sending a POST request, we have to add a -d (-data) flag. cURL allows us to send these requests in JSON format too. However, for this format to become available, we must provide additional information to notify the server that we’re sending data using a JSON format. 

  1. cURL with proxy

We can reach any destination if we combine cURL with a proxy. A proxy will route our connection through the address we input. This routing will help us visit websites that require authentications before they let us connect to them. We recommend checking the Oxylabs blog and the article they wrote about using a cURL with proxy.

  1. Protection from redirects

The greatest benefit of cURL is that it doesn’t follow redirects automatically. Our browser follows redirects by default, but if we’re using cURL, we’ll get a notice that there’s a redirect and that the document was moved.

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cURL internet protocols

Here’s a list of internet protocols that cURL supports:

  • FILE protocol;
  • DICT protocol;
  • FTP protocol;
  • FTPS protocol;
  • HTTP protocol;
  • GOPHER protocol;
  • HTTPS protocol;
  • LDAP protocol;
  • IMAP protocol;
  • IMAPS protocol;
  • MQTT protocol;
  • LDAPS protocol;
  • POP3 protocol;
  • POP3S protocol;
  • RTSP protocol;
  • RTMP protocol;
  • RTMPS protocol;
  • SCP protocol;
  • SMB protocol;
  • SFTP protocol;
  • SMBS protocol;
  • SMTP protocol;
  • TFTP protocol;
  • TELNET protocol.

Why are cURLs used for scrapping?

A web scraping procedure is basically the process that companies use to collect data from any third-party website. The main issue here is that those websites use geo-blocking and redirects as a protection measure. Why is this an issue, you may ask? 

Simply because these third-party websites can block you from entering their website, and you won’t be able to collect the data you need. That’s why a cURL can help us go around these redirects by notifying us about it.

Challenges of using these tools

There are two main challenges of using a client URL:

  1. You will need a lot of patience and effort to master the use of cURL;
  2. You can never expand to all possible use cases of cURL.

Main benefits

cURL is very useful because any relatively new operating system can use it, e.g., macOS, Linux, and Windows. If you are using anything older than Windows 10, you may have to download and install cURL because it’s not installed by default. Here are the top benefits of cURL:

  1. The cURL-help option – whenever you feel in doubt about what command to use, the cURL-help option will list all the possibilities out and give short comments with explanations for each. Still, you’ll need some background knowledge about cURL for this;
  2. Ease of use – to use cURL, you just have to open the terminal and type “curl.” After that, you can use the help option we mentioned above. You can combine the commands if you type in an URL or add the listed flags;
  3. Numerous use cases – we can use cURL for sending requests that usually get denied in online protocols, for an additional layer of protection when we face a redirect, and to connect to any destination using cURL with a proxy service.  


As you have just witnessed, cURL is an incredibly powerful tool that makes internet protocol transfers much easier for users. It has many use cases and benefits, though mastering it and learning its every possible use case is impossible. Don’t let that discourage you, though.   

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