Update Services are tools you can use to let other people know you've updated your blog. WordPress automatically notifies popular Update Services that you've updated your blog by sending a XML-RPC ping each time you create or update a post. In turn, Update Services process the ping and updates their proprietary indices with your update.
Most people use Ping-o-Matic which, with just one "ping" from you, will let many other services know that you've updated. As for why, Ping-O-Matic puts it best:
Ping-O-Matic is a service to update different search engines that your blog has updated. We regularly check downstream services to make sure that they're legit and still work. So while it may appear like we have fewer services, they're the most important ones.
If you do not want the update services to be pinged, remove all the update service URIs listed under "Update Services" on the Settings->Writing administration screen of your WordPress installation.
Certain web hosts – particularly free ones – disable the PHP functions used to alert update services. If your web host prevents pings, you should stop WordPress from attempting to ping.
http://rpc.pingomatic.com
http://rpc.twingly.com
http://www.blogdigger.com/RPC2
http://ping.blo.gs/
http://ping.feedburner.com
http://rpc.weblogs.com/RPC2
http://www.pingmyblog.com
An alternative is Feed Shark, which pings over 60 services for free.
By default, editing the Ping Services for a WordPress Multisite network site is disabled. This can be re-enabled with a plugin such as the Activate Update Services plugin.
- 2022-09-11: Original content from Update Services.