A9 has development efforts in five areas:
- Product search
- Cloud search
- Visual search
- Advertising technology
- Community question answering
A9 was created by Amazon.com in 2003 as an independent company aimed at producing technology advances in Search and Advertising. Under the direction of its first president, Udi Manber, A9 focused on several areas, including the A9.com destination website, Product Search, and a Search Advertising platform. Some early A9 services such as "Search Inside the Book" continue today, while others have been discontinued. Currently, the A9 search engine powers product search globally for Amazon.com and several other eCommerce retailers.
One purpose of A9.com was to leverage clever algorithms, and the name was chosen as a numeronym to represent ALGORITHMS (i.e. 'A' + 9 other letters).
In 2006, William Stasior, one of A9's founders and a former AltaVista and Amazon.com executive, was named president.
In 2009, A9 acquired SnapTell, an independent provider of smartphone-based visual search applications.
A9 continues to develop and operate the service that provides search on all nine Amazon.com sites around the world, as well as other retail sites owned by Amazon such as Endless.com, Javari.de, and Audible.com. In addition, A9 search is also used by other retailers, such as Marks & Spencer, that license the Amazon retail platform for their online presence.
In addition, A9 provides the "Search Inside the Book" capability for Amazon. Launched in 2003, this service allows customers to search through the full text of hundreds of thousands of books. This feature is available both for searching individual books and for the entire book catalog.
CloudSearch is a managed AWS service that makes client data searchable. For example, a business that wants to allow customers to search their catalog can upload the catalog entries to CloudSearch and then route search requests from their application or web site to the service. CloudSearch instances scale automatically, with additional servers brought online as data or traffic volume demands. Sites using CloudSearch include SmugMug, Ex.fm, and Sage Bionetworks.
The visual search group at A9 has created several mobile applications that recognize objects and allow users to find these products on Amazon.com. Their first augmented reality app, Flow, provides both object and barcode recognition. In addition, A9 visual search technology powers features to let customers search for certain products (such as shoes) by shape, and find visually similar items on Amazon.com, Zappos.com, Endless.com, and other retail sites.
A9's Advertising Technology group began delivering sponsored link advertisements on the Amazon.com retail Web site in 2003 and continues to manage this program for Amazon properties worldwide. A9 also invests in display advertising technology, including the platform that powers Amazon's ad-supported e-reader, the Kindle with Special Offers.
Community Question Answering
A9 operates Askville, a community-based question-and-answer site created in 2006. Compared with other Q&A sites, Askville focuses more on social interaction, allowing users to follow other users as well as tracking specific topics.
A9.com Search Portal
A9.com originally operated a search portal, which went live on April 14, 2004. The service featured some innovative design elements, allowing users to choose from over 400 sources to search and view results in separate columns grouped by source. In addition to web search results, users could get product search results from Amazon, encyclopedia results from Wikipedia, movie information from IMDb, and so on. Web search results were provided by different search engines over time. The search portal functionality was discontinued in 2008.
A9 developed a protocol called OpenSearch that enabled the "plug-in" search source functionality from the A9.com portal. The original specification, OpenSearch 1.0, was released in March 2005. A9 made the protocol freely available through a Creative Commons license. OpenSearch is now maintained by the OpenSearch.org community.
A9 developed the first service that allowed users of maps and Yellow Pages to view buildings at street level. Called BlockView, the service was launched in January 2005. Within a year, the service included images for 24 major U.S. cities. Both BlockView and maps were discontinued in September 2006.
In 2006, A9 launched Clickriver, an advertising program that let 3rd parties place ads on Amazon.com pages. Clickriver focused primarily on products and services that complemented Amazon's own offerings. For example, if a customer viewed a television on Amazon, a Clickriver ad might offer installation services in his or her local area. Clickriver was discontinued in 2010, replaced by other Amazon advertising programs.
- Leena Rao, "Image Recognition Startup SnapTell Acquired by Amazon Subsidiary A9.com", TechCrunch, June 16, 2009. 
- "Marks & Spencer Launches Website in Collaboration with Amazon," Computer Weekly, March 23, 2007. 
- Gary Price, "Amazon Debuts New Book Search Tool," Search Engine Watch, October 26, 2003 
- Steven Levy, "Welcome to History 2.0," Newsweek, Nov. 9, 2003
- Timothy Prickett Morgan, "Amazon Turns A9 Search Engine into a Cloud Service," The Register, Apr. 12, 2012.
- "SmugMug's Sexy New Search," SmugMug Blog, Apr. 12, 2012
- "Using Amazon CloudSearch with Python and Boto," Ex.fm Blog, Apr. 12, 2012.
- Michael Kellen, "On the Shoulders of Giants," Science, Reengineered, Apr. 14, 2012. 
- "Amazon CloudSearch - Even Better Searching for Less Than $100/Month" Amazon Web Service blog, March 2014
- Will Shanklin, "Flow for iPhone is the product ID App We Have Been Waiting For," Geek.com, Nov. 3, 2011.
- Aarthi Sivaraman, "Amazon Launches Askville.com," Reuters, Nov. 29, 2007 
- Chris Sherman, "Blending the Best of Google and Amazon", Search Engine Watch, Apr. 20, 2004. 
- Kurt Peters, "Yellow Pages Go Visual with Block View at Amazon's A9.com," Internet Retailer, Jan. 27, 2005.
- Loren Baker, "Amazon.com's Clickriver Pay-Per-Click Search Advertising," Search Engine Journal, Nov. 3, 2006.