What was the name of the technology-heavy index at the center of the dot-com crash?

The technology-heavy index at the center of the dot-com crash was the Nasdaq Composite.

The Nasdaq Composite includes thousands of companies listed on the Nasdaq Stock Market and has historically contained a large concentration of technology and internet businesses. During the late-1990s dot-com bubble, investors pushed many technology shares to extraordinary valuations despite limited profits or, in some cases, no profits at all.

The index reached a record closing level of 5,048.62 on March 10, 2000. After the bubble burst, the Nasdaq Composite fell steeply as investors reassessed business models, advertising prospects, and future earnings. The crash affected technology shares most severely, although broader markets also declined. The Nasdaq Composite is an index, not an exchange itself; Nasdaq is the marketplace, while the Composite measures the combined performance of its many listed companies.