[2] Using a mechanism known as the "snake in the tunnel", the European Exchange Rate Mechanism was an attempt to minimize fluctuations between member state currencies—initially by managing the variance of each against its respective ECU reference rate—with the aim to achieve fixed ratios over time, and so enable the European Single Currency (which became known as the euro) to replace national currencies.

[3] The move was seen by France and Germany as a wrecking tactic, especially when the increasingly Eurosceptic Thatcher announced her outright opposition to the European Economic and Monetary Union (EMU), and the idea was abandoned.

Of particular importance, the U.S. states of Illinois and New York adopted legislation to ensure a large proportion of international financial contracts recognized the euro as the successor of the ECU.

Microsoft did include the ECU symbol in many of its European versions of Windows beginning in the early 1990s; however, accessing it required the use of an Alt code, and not all typefaces provided a glyph.

Although the acronym for ECU is formed from the English name of the unit, the écu was a family of gold coins minted during the reign of Louis IX of France.