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What is CURL?

cURL is a free, open-source command-line tool for transferring data with URLs. It allows you to make requests to web servers, APIs, and other services from your terminal or within scripts. Whether you need to download a file, test an API endpoint, or automate data transfer tasks, cURL handles it through a simple command syntax. cURL supports numerous protocols including HTTP, HTTPS, FTP, FTPS, SCP, SFTP, and more. This makes it incredibly versatile for different types of network operations. You can include headers, send authentication credentials, handle cookies, set timeouts, and manage redirects, all from the command line. The tool is particularly valued by developers and system administrators who work frequently in terminal environments. Since cURL is open-source and free, it has been adopted across millions of systems and is available on Windows, macOS, Linux, and many other operating systems. It is a stable, reliable tool that has worked consistently for over two decades, making it a standard utility in development workflows and server administration.

Key Features

Multi-protocol support

HTTP, HTTPS, FTP, FTPS, SCP, SFTP, Telnet, LDAP, and more

Header customisation

Set custom headers, authentication tokens, and cookies for each request

File transfer and download

Download or upload files with progress tracking and resume capabilities

API testing

Send complex requests to APIs with various HTTP methods, data formats, and payloads

Scripting and automation

Chain commands in shell scripts to automate repetitive data transfer tasks

SSL/TLS support

Secure connections with certificate verification and advanced security options

Pros & Cons

Advantages

  • Completely free and open-source with no licensing restrictions
  • Pre-installed on most systems; minimal setup required
  • Lightweight and fast with minimal resource consumption
  • Extremely flexible with hundreds of command-line options for different scenarios
  • Extensive documentation and wide community support across decades of use

Limitations

  • Steep learning curve; command syntax can be complex for those new to command-line tools
  • No graphical interface; entirely command-line based
  • Error messages can be unclear without prior familiarity with the tool

Use Cases

Testing API endpoints during development and debugging

Downloading files or data from remote servers in automated scripts

Uploading files to servers or cloud storage services

Monitoring website availability and response times

Automating data synchronisation between systems in scheduled tasks