The dot-com bubble, also known as the dot-com boom, the tech bubble, and the Internet bubble, was a stock market bubble caused by excessive speculation of Internet-related companies in the late 1990s, a period of massive growth in the use and adoption of the Internet.Between 1995 and its peak in March 2000, the Nasdaq Composite stock market index rose 400%, only to fall 78% from its peak by October 2002, giving up all its gains during the bubble. During the dot-com crash, many online shopping companies, such as Pets.com, Webvan, and Boo.com, as well as several communication companies, such as Worldcom, NorthPoint Communications, and Global Crossing, failed and shut down. Some companies that survived, such as Amazon.com, lost large portions of their market capitalization, with Cisco Systems alone losing 80% of its stock value.

The Nasdaq Composite (ticker symbol ^IXIC) is a stock market index that includes almost all stocks listed on the Nasdaq stock exchange. Along with the Dow Jones Industrial Average and S&P 500, it is one of the three most-followed stock market indices in the United States. The composition of the NASDAQ Composite is heavily weighted towards companies in the information technology sector. The Nasdaq-100, which includes 100 of the largest non-financial companies in the Nasdaq Composite, accounts for over 90% of the movement of the Nasdaq Composite.

The Nasdaq Composite is a capitalization-weighted index; its price is calculated by taking the sum of the products of closing price and index share of all of the securities in the index. The sum is then divided by a divisor which reduces the order of magnitude of the result.