an advertising technique used on websites, advertising networks, and search engines.

With search engines, pay per click advertisements are usually text ads placed near search results; when a site visitor clicks on the advertisement, the advertiser is charged a small amount. Variants include pay for placement and pay for ranking. Pay per click is also sometimes known as Cost Per Click (CPC).

While many companies exist in this space, Google Adwords and Yahoo! Search Marketing, which was formerly Overture, are the largest network operators as of 2006. MSN has started beta testing with their own PPC services MSN adCenter. Depending on the search engine, minimum prices per click start at US$0.01 (up to US$0.50). Very popular search terms can cost much more on popular engines. Abuse of the pay per click model can result in click fraud. Click fraud is usually not detected very well by smaller PPC engines.