Co-founded by Rich Skrenta in 2007, Blekko was a search engine that provided search results without irrelevant links. Using a Google-style search algorithm, Blekko users had the option of selecting the types of websites they wanted to see in their search results.
To weed out pages created by content farms, Blekko editors prescreened all Blekko search results. This enabled users who entered searches for categories such as finance, hotels, health and cars to receive results from credible sources. Other Blekko features included site comparison, search engine optimization statistics, IP address lookup, and page tagging and duplicate content check.
To perform a search and categorize searches on Blekko, slashtags consisting of a text tag preceded by a "/" slash were used. Slashtags were automatically added on all search categories with prescreened results. The use of slashtags restricted search results to those matching specific characteristics. On Blekko, all health-related queries were limited to a prescreened list of trustworthy sites determined by Blekko editors.
To reduce spam and perform customized searches, users had the option of creating slashtags after sign up. In 2015, IBM acquired Blekko and Blekko's Web-crawling abilities were integrated into IBM Watson. In addition, Blekko's technology is being utilized to crawl the Web and deliver data to the AlchemyAPI technology, which enables Watson's existing systems to deliver information to users.