Which UK stock market index is nicknamed the "Footsie"?

The UK stock market index nicknamed the “Footsie” is the FTSE 100.

Its name is formed from the initials of the Financial Times and the London Stock Exchange, the organizations associated with its creation. The index began on January 3, 1984, and tracks 100 of the largest companies listed on the London Stock Exchange by market capitalization. Because it is widely followed as a barometer of major British-listed businesses, “Footsie” became a familiar informal nickname.

The FTSE 100 is a capitalization-weighted index, so larger companies generally have more influence on its movements than smaller constituents. Its companies are often described as blue-chip stocks, although many earn substantial revenue outside the United Kingdom.

The main mix-up is with the FTSE 250, which covers medium-sized companies ranked below the FTSE 100 constituents. The FTSE 350 combines the FTSE 100 and FTSE 250, while the FTSE All-Share is a broader measure of the UK equity market.