HTTP Keep-Alives

Last Edited



Definition of HTTP Keep-Alives in the Network Encyclopedia.

What is HTTP Keep-Alives?

HTTP Keep-Alives is an enhanced version of HTTP persistent connections supported by Microsoft Internet Information Server (IIS). HTTP Keep-Alives allow a client Web browser to keep connections open with the Web server instead of closing them after the request has been answered and reopening them for each new Hypertext Transfer Protocol (HTTP) request, which consumes system resources.

For this feature to work, however, both the client Web browser and the Web server must support HTTP Keep-Alives.

Keep-Alive enable and disable

Web browsers that support this feature include Microsoft Internet Explorer version 2 and later and Netscape Navigator 2 and later.

TCP Keep-Alives

HTTP Keep-Alives are enabled by default. They are not the same as TCP Keep-Alives, which are periodic packets sent between machines to determine whether an idle connection is still active.

»» To read next: Know the difference between port 443 and port 80.

Advantages of enabling Keep-Alive:

  • Keep-Alive reduces the usage of CPU and memory due to a smaller amount of generated HTTP requests. This will benefit all hosting platform users (free hosting, shared hosting, VPS)
  • Enabling Keep-Alive provides HTTP pipelining (delivery of requests via same TCP connection)
  • HTTPS requests need more CPU time and resources. Keep-Alive will greatly benefit your website if you use HTTPS and SSL.
  • Reduced latency and overall increase in loading speed and performance.
  • Keep-Alive is supported by all modern browsers
  • Enabling Keep-Alive will also benefit your website in terms of SEO and ranking due to better site performance.

See also: