Keep Alive, A client has to create a new connection to interact and receive a file from a server

1. The client requests an HTML file using a new connection and this connection terminates after receiving the file
2. The browser interprets the HTML file and checks whether any other files are required to display the complete web page
3. After a thorough analysis, it creates a new connection to request each of those files

How HTTP Works Without Keep-Alive

A single HTML page may contain several resources that make up the entire web page. This includes HTML code, CSS files, JavaScript files, images, and multimedia files. For instance, if the HTML has 4 stylesheets, 2 Javascript files, and 3 image files, this indicates an additional 9 requests to get these files. But this mechanism is very inefficient, especially with complex web pages that have a large number of elements.

The Need for Keep-Alive

Creating multiple connections may reduce the loading time. It also utilizes many resources on the server. We can eventually overcome this issue and transfer all those files through a single connection by enabling the Keep-Alive, which avoids the need to repeatedly open and close a new connection. If it is not enabled, the process could take considerably longer to display the web page.

How to Enable Keep-Alive

Keep-Alive (also known as HTTP Keep-Alive or persistent connection) is a bit of communication (message) between the client and server that says: “You may grab many files.” These are extremely small messages that consume very little bandwidth. The following method assumes Apache webserver.

Keep-Alive is enabled by explicitly requesting it via HTTP header. If you don’t have access to your web server configuration file, you can add HTTP headers yourself by using the .htaccess file.

The .htaccess file is a configuration control file that will take effect when placed in any directory, which is in turn loaded via the Apache server. You may create a .htaccess file using any text editor such as a TextPad or gedit (Linux). It’s a method to reconfigure your website without altering the server configuration file. This is done by overriding its original configuration without having to restart the webserver when changes are made.