We will start installing command-line tools. One of the key advantages of command-line tools is that you can easily run again the HTTP requests again after we have built them for the first time, and we don't need to use the mouse or tap the screen to run requests. We can also easily build a script with batch requests and run them.

As happens with any command-line tool, it can take more time to perform the first requests compared with GUI tools, but it becomes easier once we have performed many requests and we can easily reuse the commands we have written in the past to compose new requests.

Curl, also known as cURL, is a very popular open source command-line tool and library that allows us to easily transfer data. We can use the curl command-line tool to easily compose and send HTTP requests and check their responses.

In Linux or macOS, you can open a Terminal and start using curl from the command line.

In Windows, you have two options. You can work with curl in Command Prompt or you can decide to install curl as part of the Cygwin package installation option and execute it from the Cygwin terminal. You can read more about the Cygwin terminal and its installation procedure at: http://cygwin.com/install.html. Windows Powershell includes a curl alias that calls the Invoke-WebRequest command, and therefore, if you want to work with Windows Powershell with curl, it is necessary to remove the curl alias.

If you want to use the curl command within Command Prompt, you just need to download and unzip the latest version of the curl download page: https://curl.haxx.se/download.html. Make sure you download the version that includes SSL and SSH.

The following screenshot shows the available downloads for Windows. The Win64 - Generic section includes the versions that we can run in Command Prompt or Windows Powershell.

The Win64 x86_64.7zip file provides the binary version for curl version 7.55.1 with SSL and SSH support:

After you unzip the .7zip or .zip file you have downloaded, you can include the folder in which curl.exe is included in your path. For example, if you unzip the Win64 x86_64.7zip file, you will find curl.exe in the bin folder. The following screenshot shows the results of executing curl --version on  Command Prompt in Windows 10. The --version option makes curl display its version and all the libraries, protocols, and features it supports: