Many blog authoring tools automatically ping one or more servers each time the blogger creates a new post (or updates an old one.) That is, the tool sends an XML-RPC signal to one or more "ping servers," that can then generate a list of blogs that have new material.

Open ping servers, like VeriSign's Weblogs.com and Yahoo!'s blo.gs, let other web-services subscribe to a list of blogs that have recently pinged them. Blog search engines can provide fresh results very quickly by polling only the newly-updated blogs. Similarly, aggregators use results from ping servers to tell subscribers which items on their subscription lists have fresh material. A few of the blog aggregators that can be pinged directly include: BulkFeeds, FeedBurner, Google Blog Search, IceRocket, Technorati, Yahoo and BlogBlogs.

In addition to open ping servers, there are an increasing number of proprietary ping servers that gather information only for their own applications. Most of the major blog search engines operate such ping servers.

There is a conflict of interest here between the blogger--who wants his new post to get the widest possible publicity as fast as possible--and the web-service owner--who wants his search engine or aggregator to have new blog posts long before anyone else. As a result, bloggers have turned to services such as Ping-o-matic, which pings multiple proprietary ping servers. As the blogosphere has grown, other ping "services" have cropped up, such as Ping , Pingoat and BlogFlux Pinger.

Ping spam

The use of ping servers to direct attention to recent blog posts has led to a rash of ping spam or sping, which attempts to direct readers to web pages that are not, in fact, recent blog posts. Examples:

Product vendors who use a weblog-like format to post product ads, meaningless batches of Google keywords, etc.

Software vendors, who sell scripts that make automated "weblog postings" every hour around the clock.

Creators of ping spam and/or spam blogs may hope to benefit by creating pages to turn up in web searches for popular keywords. Typically, an individual spam post links to some external page that displays Google ads or offers a product for sale.